Connector terminal material and manufacturing method thereof

Abstract

Not only does it maintain a low coefficient of friction, but it also improves resistance to fretting wear. [Solution] A coating is formed on the surface of a substrate made of copper or a copper alloy, and the coating has a nickel layer made of nickel or a nickel alloy formed on the surface of the substrate, a copper-tin alloy layer made of an alloy of copper and tin formed on the nickel layer, and a tin layer made of tin or a tin alloy formed on the copper-tin alloy layer, wherein the average thickness of the nickel layer is 0.30 μm to 3.00 μm, the average thickness of the copper-tin alloy layer is 0.30 μm to 1.20 μm, and the average thickness of the tin layer is 0.15 μm to 0.80 μm, and the copper-tin alloy layer contains a Cu6Sn5 alloy whose interface with the tin layer forms an uneven shape, the average thickness of the convex portions of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate is 0.80 μm to 3.00 μm, and the average KAM of the Cu6Sn5 alloy in a cross section parallel to the rolling direction is 0.55° to 0.80°.

Description

[Technical Field]

[0001] The present invention relates to a terminal material for a connector having fretting wear resistance and a method for producing the same. [Background technology]

[0002] Conventionally, connectors used to connect electrical wiring in automobiles, consumer devices, etc. have terminal pairs designed to be electrically connected when a contact piece provided on the female terminal comes into contact with a male terminal inserted into the female terminal at a predetermined contact pressure.

[0003] As such a connector (terminal), a terminal material is known in which a copper or copper alloy substrate is copper-plated and tin-plated, and then a reflow process is performed to form a copper-tin alloy layer and a tin layer on the substrate.

[0004] For example, in Patent Document 1, the insertion force is reduced by making the tin layer made of tin or a tin alloy on the copper-tin alloy layer very thin, but there is a problem in that the contact resistance increases in high-temperature environments because the tin layer is so thin.

[0005] Furthermore, in Patent Document 2, a portion of the copper-tin alloy is replaced with nickel to give the copper-tin alloy a steeply uneven shape, and a tin layer is left behind, thereby reducing friction and preventing an increase in contact resistance during heating. However, because the copper-tin alloy layer is steep, there is a limit to how much friction can be reduced.

[0006] On the other hand, in Patent Document 3, a nickel-tin alloy layer made of Ni3Sn4 is formed instead of a copper-tin alloy layer, but the alloy shape is long and thin, and when the alloy containing nickel oxidizes, the resistance increases significantly, resulting in insufficient connection reliability and fretting wear resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-012320 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-240520 [Patent Document 3] Japanese Patent Publication No. 2020-056056 Summary of the Invention [Problem to be solved by the invention]

[0008] In these terminal materials, the soft tin layer on the surface is prone to adhesion during insertion and removal, which means that the insertion force is likely to be high. Even if a hard alloy layer such as a copper-tin alloy layer or a nickel-tin alloy layer is formed under the tin layer, the shape cannot be optimized, and there is a problem that the resistance to fretting wear is still insufficient when used to connect electrical wiring in automobiles, consumer devices, etc., where fretting wear occurs.

[0009] The present invention has been made in view of the above circumstances, and has as its object not only to maintain a low coefficient of friction but also to improve fretting wear resistance. [Means for solving the problem]

[0010] The terminal material for a connector of the present invention has a coating formed on the surface of a substrate made of copper or a copper alloy, and the coating has a nickel layer made of nickel or a nickel alloy formed on the surface of the substrate, a copper-tin alloy layer made of an alloy of copper and tin formed on the nickel layer, and a tin layer made of tin or a tin alloy formed on the copper-tin alloy layer, and the average thickness of the nickel layer is 0.30 μm or more and 3.00 μm or less, and the average thickness of the copper-tin alloy layer is 0.3 The copper-tin alloy layer has a Cu6Sn5 alloy whose interface with the tin layer has an uneven shape, the average thickness of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate is 0.80 μm or more and 3.00 μm or less, and the average KAM of the Cu6Sn5 alloy in a cross section parallel to the rolling direction is 0.55° or more and 0.80° or less.

[0011] The nickel layer functions as a barrier to prevent the diffusion of copper and other components (substrate components) from the substrate at high temperatures, improving heat resistance. The greater the average thickness of this nickel layer, the higher the heat resistance, but a certain thickness is unnecessary and prone to cracking during processing, so the upper limit was set at 3.00 μm. On the other hand, if the average thickness of the nickel layer is less than 0.30 μm, the barrier function against substrate components will be insufficient, resulting in high contact resistance in high-temperature environments.

[0012] In addition, the copper-tin alloy layer and the tin layer have a composite structure in which the relatively soft tin layer on the surface is supported by the hard copper-tin alloy layer, and the interface between them has an uneven shape, which, combined with the lubricating effect of the tin layer, reduces the coefficient of friction. In this case, if the average thickness of the copper-tin alloy layer exceeds 1.20 μm, the uneven shape of the Cu6Sn5 alloy becomes non-uniform, the average value of KAM (Kernel Average Misorientation) of the Cu6Sn5 alloy decreases, the copper-tin alloy layer becomes difficult to slide during sliding, and fretting wear resistance decreases. On the other hand, if the average thickness of the copper-tin alloy layer is less than 0.30 μm, the hard copper-tin alloy layer will be reduced, resulting in a high coefficient of friction and a decrease in fretting wear resistance.

[0013] If the average thickness of the tin layer exceeds 0.80 μm, adhesive wear is more likely to occur, resulting in a high coefficient of friction. Conversely, if the average thickness of the tin layer is less than 0.15 μm, there is less of the tin layer with a lubricating effect, resulting in a high coefficient of friction and high contact resistance in high-temperature environments.

[0014] Furthermore, the higher the average KAM value of the Cu6Sn5 alloy, the more small-angle grain boundaries with a misorientation of 5° or less are formed, making it less likely to deform. This reduces wear on the copper-tin alloy layer during sliding, resulting in good fretting wear resistance. However, because stress is released during reflow, it is difficult to produce a coating with an angle of more than 0.80°. On the other hand, if the average value of KAM is less than 0.55°, the strain is reduced and the copper-tin alloy layer is more likely to deform during sliding, resulting in an increased coefficient of friction and reduced fretting wear resistance.

[0015] If the average thickness of the Cu6Sn5 alloy projections exceeds 3.00 μm, the average KAM value will decrease and the Cu6Sn5 alloy will have an uneven asperity, resulting in a high coefficient of friction and reduced freight wear resistance.If the average thickness of the projections is less than 0.80 μm, the thickness of the copper-tin alloy layer will be thin, resulting in a high coefficient of friction and reduced freight wear resistance.

[0016] In the terminal material for a connector of the present invention, the curvature radius of the surface of the convex portion of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate may be 0.40 μm or more and 2.00 μm or less.

[0017] If the curvature radius of the convex surface of the Cu6Sn5 alloy exceeds 2.00 μm, the Cu6Sn5 alloy will slide more frequently against itself when used as a connector, reducing the effectiveness of the tin layer, which acts as a lubricant, and the coefficient of friction will increase, resulting in a tendency for freight wear resistance to decrease.On the other hand, if the curvature radius is less than 0.40 μm, the sliding contact points between the Cu6Sn5 alloy pieces will be fewer and less uniform when used as a connector, resulting in a tendency for the coefficient of friction to increase and freight wear resistance to decrease.

[0018] The terminal material for a connector of the present invention preferably has a connecting portion to be connected to a mating part and a board fixing portion to be fixed to a board, and the coating is formed at least on the connecting portion. In this case, it is preferable that the substrate fixing portion has a tin surface layer made of tin or a tin alloy formed on the entire surface, rear surface and both side surfaces.

[0019] By forming the above-mentioned coating at least on the connection portion, the terminal has excellent insertability and extractability. Furthermore, for terminal materials for connectors that require fixing to a substrate, it is preferable to use a "post-plating method" in which plating is performed after punching out a metal plate, and it is preferable that the above-mentioned coating is formed at least on the connection portion that is connected to the other side, and that a tin surface layer made of tin or a tin alloy is formed on the entire surface of at least the fixing portion to the substrate. In the case of pin-shaped terminals, a tin surface layer made of tin or a tin alloy is formed on the entire surface of the board fixing part, which gives the terminal excellent solderability, and the formation of the above-mentioned coating at the connection part with the mating part makes the terminal excellent in insertion and removal properties.

[0020] The method for manufacturing a terminal material for a connector of the present invention includes a plating layer forming step of laminating a nickel plating layer made of nickel or a nickel alloy, a copper plating layer made of copper or a copper alloy, and a tin plating layer made of tin or a tin alloy in this order on a surface of a substrate made of copper or a copper alloy to form a substrate with plating layers, and a reflow treatment step of heating the substrate with plating layers to perform a reflow treatment, The reflow treatment step includes a first heating treatment in which the base material with the plating layer is heated at a furnace temperature of 240°C to 380°C for a time period of 5 to 30 seconds to melt the tin plating layer, and a second heating treatment in which the base material with the plating layer is heated at a furnace temperature of 150°C to 235°C for a time period of 10 to 60 seconds after the first heating treatment. By cooling after the second heating treatment, a coating is formed on the base material, which is composed of a nickel layer made of nickel or a nickel alloy and having an average thickness of 0.30 μm to 3.00 μm, a copper-tin alloy layer made of an alloy of copper and tin and having an average thickness of 0.30 μm to 1.20 μm, and a tin layer made of tin or a tin alloy and having an average thickness of 0.15 μm to 0.80 μm, laminated in this order.

[0021] By performing the reflow treatment process as a two-stage heating process under predetermined temperature conditions followed by cooling, the average value of the KAM of the Cu6Sn5 alloy in the copper-tin alloy layer, the average value of the thickness of the protrusions, and the radius of curvature of the surface of the protrusions can be controlled within predetermined ranges. Note that although the plating layer changes during the reflow treatment process, the substrate is referred to as a substrate with a plating layer until the reflow treatment process is completed.

[0022] If the furnace temperature or heating time of the first heat treatment is below the lower limit, the growth of the copper-tin alloy layer will be insufficient, the protrusions of the Cu6Sn5 alloy will be thin, the coefficient of friction will be high, and fretting wear resistance will be reduced. If the furnace temperature or heating time of the first heat treatment exceeds the upper limit, the copper-tin alloy layer grows excessively, the Cu6Sn5 alloy protrusions become too thick, the copper-tin alloy layer becomes too thick, the remaining tin layer becomes thin, and the lubricating tin layer becomes less. As a result, the friction coefficient increases and contact resistance increases in high-temperature environments. Furthermore, the Cu6Sn5 alloy's uneven shape becomes uneven and the curvature radius of the protrusions becomes large, making it difficult for the copper-tin alloy layer to slide during sliding, which tends to reduce fretting wear resistance. The average KAM of the Cu6Sn5 alloy also decreases slightly.

[0023] If the furnace temperature or heating time of the second heating treatment is below the lower limit, the Cu6Sn5 alloy will not grow to a sufficient size, the thickness of the Cu6Sn5 alloy protrusions will be thin, the thickness of the copper-tin alloy layer will be thin, the friction coefficient will be high, and freight wear resistance will be reduced. Furthermore, the Cu6Sn5 alloy will have a pointed shape and a small radius of curvature, which will tend to slightly increase the friction coefficient and reduce freight wear resistance. If the furnace temperature or heating time of the second heat treatment exceeds the upper limit, the growth of the copper-tin alloy becomes excessive, the convex parts of the Cu6Sn5 alloy become too thick, and the Cu6Sn5 alloy's uneven shape becomes uneven, resulting in an increase in the friction coefficient and a decrease in freight wear resistance. Furthermore, the curvature radius of the convex parts becomes larger, which increases the friction coefficient and tends to decrease freight wear resistance. The average KAM of the Cu6Sn5 alloy also becomes slightly lower.

[0024] In the manufacturing method of terminal material for connectors of the present invention, it is preferable to have a punching process before the plating layer forming process, in which a metal plate is punched to form a terminal chain body in which a plurality of terminal members are formed at intervals in the longitudinal direction of the elongated carrier portion.

[0025] Since the punching process is carried out before the plating layer formation process, a coating is formed not only on the front and back surfaces of the terminal member but also on the punched cut end surfaces (side surfaces), allowing the terminal to exhibit stable characteristics regardless of the orientation in which it is used. [Effects of the Invention]

[0026] According to the present invention, by controlling the average thickness of the copper-tin alloy layer and the tin layer and by controlling the average thickness of the Cu6Sn5 alloy protrusions and the average KAM within a predetermined range, it is possible to not only maintain a low friction coefficient but also improve fretting wear resistance. Furthermore, by setting the nickel layer and the tin layer to a predetermined average thickness, it is possible to reduce contact resistance in high-temperature environments. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a plan view of a terminal material for a connector according to an embodiment of the present invention; [Figure 2] 2 is a schematic cross-sectional view of the connector terminal material of FIG. 1. [Figure 3] 2 is a flowchart showing a method for manufacturing the connector terminal material of FIG. 1. [Figure 4] 3 is a schematic cross-sectional view showing a substrate with a plating layer before a reflow treatment step of the terminal material for a connector of FIG. 2. FIG. [Figure 5] 1 is a backscattered electron (BSE) image of a cross section of Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0029] [Configuration of connector terminal materials] As shown in Figure 1, the terminal material 1 for connectors in this embodiment is a terminal chain formed by connecting multiple terminal members 10 in the shape of pin terminals, and is formed by punching out a long plate material using a press process. Specifically, a plurality of elongated terminal members 10 are provided in parallel at predetermined intervals on one side of an elongated connecting member 11 of a predetermined width, extending in a direction perpendicular to the longitudinal direction of the connecting member 11. Each terminal member 10 has a pin-shaped connecting portion 13 and a board fixing portion 14, which is narrower than the connecting portion 13, formed continuously from its tip, and the base end of the board fixing portion 15 is connected at a right angle to the connecting member 11. After being separated from the connecting member 11, the terminal member 10 is used by fixing the board fixing portion 15 to a board or the like in an electrically connected state by press-fitting or soldering it into a through-hole or the like in the board, and the electrical connection is made by inserting the connecting portion 13 into another female terminal. The shape of the terminal member 10 is merely an example and is not limited to that shown in FIG. 1, and may be any shape as long as it has a connection portion for electrical connection with a mating terminal.

[0030] As shown in the cross section of FIG. 2, this connector terminal material 1 has a coating 22 formed on a substrate 21 made of copper or a copper alloy, and the coating 22 is made up of a nickel layer 23 made of nickel or a nickel alloy, a copper-tin alloy layer 24 made of an alloy of copper and tin, and a tin layer 25 made of tin or a tin alloy, which are formed in this order. FIG. 2 shows a cross section of the substrate 21 parallel to the rolling direction, and the coating 22 is formed on the entire surface of both the front and rear surfaces and both side surfaces of the substrate 21.

[0031] The composition of the substrate 21 is not particularly limited as long as it is made of copper or a copper alloy, and it may be made of a plate material made of copper or a copper alloy such as oxygen-free copper (C10200), Cu-Mg copper alloy (C18665), brass, or phosphor bronze.

[0032] The nickel layer 23 has the function of suppressing the diffusion of components (substrate components) such as copper from the substrate 21 into the copper-tin alloy layer 24 and tin layer 25 formed thereon. The average thickness (film thickness) of the nickel layer 23 is 0.30 μm or more and 3.00 μm or less. If the average thickness of the nickel layer 23 is less than 0.30 μm, copper will diffuse from the substrate 21 in a high-temperature environment, resulting in an increase in contact resistance. The greater the average thickness of the nickel layer 23, the higher the heat resistance, but a certain thickness is not necessary. If the average thickness of the nickel layer 23 exceeds 3.00 μm, cracks may occur during bending. The composition of the nickel layer 23 is not particularly limited as long as it is made of nickel or a nickel alloy.

[0033] The copper-tin alloy layer 24 is obtained by sequentially forming a copper plating layer and a tin plating layer on the nickel layer 23 and then performing a reflow treatment, and is formed of a composite structure consisting of only a Cu6Sn5 alloy or a majority of a Cu6Sn5 alloy with a small amount of a Cu3Sn alloy disposed thereunder. The surface of this copper-tin alloy layer 24, i.e., the interface with the tin layer 25 thereon, is formed in an uneven shape, and a part of it is exposed on the surface of the tin layer 25. The average thickness of this copper-tin alloy layer 24 is 0.30 μm or more and 1.20 μm or less. Furthermore, for the Cu6Sn5 alloy in the copper-tin alloy layer 24, the average thickness of the protrusions in a cross section parallel to the rolling direction of the base material 21 is 0.80 μm or more and 3.00 μm or less, and the average KAM of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the base material 21 is 0.55° or more and 0.80° or less. Furthermore, the radius of curvature of the surface of the protrusions of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the base material 21 is preferably 0.40 μm or more and 2.00 μm or less.

[0034] The average thickness of the Cu6Sn5 alloy protrusions of the copper-tin alloy layer 24 and the average KAM are affected by the reflow treatment conditions and the thickness of the copper-tin alloy layer 24, which will be described later. If the furnace temperature or heating time of the first heating treatment in the reflow process falls below the lower limit, the growth of the copper-tin alloy layer 24 becomes insufficient, the Cu6Sn5 alloy protrusions become thin, the friction coefficient increases, and fretting wear resistance decreases. If the Cu6Sn5 alloy protrusions become too thick and the average thickness of the copper-tin alloy layer 24 becomes too large, the tin layer becomes relatively thin, and the lubricating tin layer becomes less. As a result, the friction coefficient increases and contact resistance increases in high-temperature environments. Furthermore, the Cu6Sn5 alloy's uneven shape becomes non-uniform, and the radius of curvature of the protrusion surface becomes small, making it difficult for the copper-tin alloy layer to slide during sliding, which tends to reduce fretting wear resistance. The average KAM (kernel average misorientation) of the Cu6Sn5 alloy also decreases slightly. If the furnace temperature or heating time of the second heating treatment in the reflow treatment is below the lower limit, the Cu6Sn5 alloy does not grow to a sufficient size, the thickness of the Cu6Sn5 alloy protrusions becomes thin, the thickness of the copper-tin alloy layer becomes thin, the friction coefficient increases, and freight wear resistance decreases. Furthermore, because the Cu6Sn5 alloy has a pointed shape and a small radius of curvature, the friction coefficient increases slightly, and freight wear resistance tends to decrease. If the furnace temperature or heating time of the second heat treatment exceeds the upper limit, the growth of the copper-tin alloy layer 24 becomes excessive, resulting in excessively thick convex portions of the Cu6Sn5 alloy and an uneven shape of the Cu6Sn5 alloy, which increases the coefficient of friction and reduces fretting wear resistance. Furthermore, the curvature radius of the convex portions increases, increasing the coefficient of friction and reducing fretting wear resistance. The average KAM of the Cu6Sn5 alloy also tends to decrease slightly. The furnace temperature for this second heat treatment is preferably 170°C or higher and 220°C or lower.

[0035] If the average thickness of the Cu6Sn5 alloy projections in the copper-tin alloy layer exceeds 3.00 μm, the average KAM of the Cu6Sn5 alloy will decrease and the Cu6Sn5 alloy will have a non-uniform asperity shape, resulting in a high friction coefficient and reduced freight wear resistance.If the average thickness of the projections is less than 0.80 μm, the copper-tin alloy layer will be too thin and freight wear resistance will be reduced. Furthermore, if the curvature radius of the convex surface of the Cu6Sn5 alloy exceeds 2.00 μm, the copper-tin alloy layers will slide more frequently when sliding as a connector, reducing the effectiveness of the tin layer acting as a lubricant, resulting in a higher coefficient of friction and a lower freight wear resistance.On the other hand, if the curvature radius is less than 0.40 μm, the copper-tin alloy layers will slide less and less uniformly when sliding as a connector, resulting in a higher coefficient of friction and a lower freight wear resistance.

[0036] The average KAM (Kernel Average Misorientation) value of Cu6Sn5 alloy is measured by EBSD (Electron Backscattered Diffraction) method. It is the average value of the misorientation between adjacent measurement points and represents the local change in crystal orientation. The larger the average KAM value, the larger the distortion. The higher the average KAM value of this Cu6Sn5 alloy, the more small-angle grain boundaries with a misorientation of 5° or less are formed, making it less likely to deform. This reduces wear on the copper-tin alloy layer during sliding and improves fretting wear resistance, but because stress is released during reflow, it is difficult to produce a coating with an angle of more than 0.80°. On the other hand, if the average KAM value of the Cu6Sn5 alloy is less than 0.55°, the strain is reduced and the copper-tin alloy layer is more likely to deform during sliding, resulting in an increased friction coefficient and reduced fretting wear resistance.

[0037] The tin layer 25 is made of tin or a tin alloy and has an average thickness of 0.15 μm to 0.80 μm. If the average thickness of the tin layer exceeds 0.80 μm, adhesive wear is more likely to occur, resulting in a high coefficient of friction. Conversely, if the average thickness of the tin layer is less than 0.15 μm, the tin layer having a lubricating effect is less, resulting in a high coefficient of friction and high contact resistance in high-temperature environments.

[0038] [Method of manufacturing connector terminal material] Next, a method for manufacturing this connector terminal material 1 will be described. The manufacturing method of this connector terminal material 1 includes a punching step of punching a long, thin metal plate with a press to form a chain of terminals that will become the base material 21, a pretreatment step of cleaning the surface of the base material 21 after punching, a plating layer forming step of forming a nickel plating layer 31, a copper plating layer 32, and a tin plating layer 33 in that order on the surface of the base material 21, and a reflow treatment step of heating the plated-layer-coated base material 35 on which the three plating layers 31 to 33 have been formed, for a reflow treatment (see FIG. 3). The steps will be explained below in order.

[0039] (Punching process) A thin metal plate made of copper or a copper alloy wound into a coil is punched out by a press while being unwound, to form a chained-terminals body that serves as a base material 21 as shown in FIG.

[0040] (Pretreatment process) After punching, the base material 21 is subjected to pre-treatment such as degreasing and pickling to clean the surface.

[0041] (Plating layer formation process) After the pretreatment, a nickel plating layer 31 made of nickel or a nickel alloy, a copper plating layer 32 made of copper or a copper alloy, and a tin plating layer 33 made of tin or a tin alloy are formed in this order on the substrate 21 as follows (see FIG. 4).

[0042] -Nickel plating layer- The pretreated surface of the substrate 21 is then subjected to nickel plating to form a nickel plating layer 31 made of nickel or a nickel alloy. A typical nickel plating bath may be used, for example, a sulfamic acid bath containing nickel sulfamate and boric acid as the main components. The temperature of the plating bath is 50°C to 60°C, and the current density is 1 A / dm 2 More than 10A / dm 2 The following is said to be true.

[0043] -Copper plating layer- Copper plating is performed on the nickel plating layer 31 to form a copper plating layer 32 made of copper or a copper alloy. A common copper plating bath may be used for copper plating, such as a copper sulfate bath containing copper sulfate and sulfuric acid as its main components. The temperature of the plating bath is 20°C to 50°C, and the current density is 1 A / dm 2 More than 10A / dm 2 The following is said to be true.

[0044] -Tin plating layer- A tin plating process is carried out on the copper plating layer 32 to form a tin plating layer 33 made of tin or a tin alloy. A common tin plating bath may be used as the plating bath for forming the tin plating layer 33, such as a methanesulfonic acid bath containing methanesulfonic acid and tin methanesulfonate as the main components. The temperature of the plating bath is 20°C to 40°C, and the current density is 1 A / dm 2 More than 20A / dm 2 The following is said to be true.

[0045] In this way, a nickel plating layer 31, a copper plating layer 32, and a tin plating layer 33 are sequentially formed on the surface of the substrate 21, thereby obtaining a substrate 35 with plating layers, in which three plating layers 31 to 33 are laminated. Note that a cleaning treatment using sulfuric acid or the like is performed between each plating treatment. Before this plating process, the substrate 21 is in a state where it has been punched into a chain terminal body by a press, and the substrate 21 is then immersed in a plating bath to form the plating layers 31-33, so that the three plating layers 31-33 are formed not only on the front and back surfaces of the substrate 21 but also on both side surfaces (the cut end surfaces during punching). However, the present invention can also be used in a "partial plating" process in which only a portion of the substrate is immersed in a plating bath.

[0046] (Reflow processing process) The plated layer-equipped substrate 35 having the plated layers 31 to 33 formed thereon as described above is subjected to a reflow treatment. In the case of a long, narrow plate material (strip material) wound on a roll, this reflow treatment is performed by running the plate material in the lengthwise direction and passing it through a reflow furnace while continuously performing the above-described pretreatment and plating treatment. However, in the case of the plated layer-equipped substrate 35 of this embodiment, it is a punched material that has been punched out in advance by a press into a chain of terminals of a predetermined length as shown in Fig. 1, and after the punched material is subjected to the above-described pretreatment and plating treatment, the plated layer-equipped substrate 35 is supplied to a relatively small reflow furnace and subjected to the reflow treatment.

[0047] The reflow treatment process includes a first heating treatment in which the substrate 35 with a plating layer is passed through a first heating furnace, the furnace temperature of which is 240°C or more and 380°C or less, for a period of 5 seconds or more and 30 seconds or less, thereby heating the substrate 35 to above the melting point of tin and melting the tin plating layer, and a second heating treatment in which the substrate 35 with a plating layer is passed through a second heating furnace, the furnace temperature of which is set to 150°C or more and 235°C or less, for a period of 10 seconds or more and 60 seconds or less, and the substrate 35 is cooled after the second heating treatment.

[0048] In this reflow treatment, the tin plating layer 33 is melted by heating to a high temperature in a first heating treatment, and then maintained at a low temperature below the melting point of tin, thereby controlling the shape of the interface between the copper-tin alloy layer 24 and the tin layer 25, and controlling the average value of the KAM of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate 21, the average value of the thickness of the convex portions of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate, and the radius of curvature of the convex portion surface within predetermined ranges, thereby reducing the coefficient of friction.

[0049] In this case, if the furnace temperature is below 240°C or the heating time is less than 5 seconds, the heating is insufficient, the copper-tin alloy layer 24 does not grow sufficiently, and the Cu6Sn5 alloy protrusions at the interface with the tin layer 25 become thin, resulting in a high friction coefficient and reduced fretting wear resistance. On the other hand, if the furnace temperature exceeds 380°C or the heating time exceeds 30 seconds, the copper-tin alloy layer grows excessively, the Cu6Sn5 alloy protrusions become too thick, the copper-tin alloy layer becomes too thick, the remaining tin layer becomes thin, and the lubricating tin layer becomes less. As a result, the friction coefficient increases and contact resistance in high-temperature environments increases. Furthermore, the Cu6Sn5 alloy's uneven shape and the curvature radius of the protrusions become large, which makes it difficult for the copper-tin alloy layer to slide during sliding, tending to reduce fretting wear resistance. The average KAM of the Cu6Sn5 alloy also becomes slightly lower.

[0050] Furthermore, in the second heating treatment, if the furnace temperature is below 150°C or the heating time is less than 10 seconds, the Cu6Sn5 alloy does not grow to a sufficient size, the thickness of the convex portions is thin, the thickness of the copper-tin alloy layer is thin, the friction coefficient is high, and freight wear resistance is reduced. Furthermore, the Cu6Sn5 alloy has a pointed shape and a small radius of curvature, which tends to slightly increase the friction coefficient and reduce freight wear resistance. On the other hand, if the furnace temperature in the second heating treatment exceeds 235°C or the heating time exceeds 60 seconds, the growth of the copper-tin alloy becomes excessive, the convex portions of the Cu6Sn5 alloy become too thick, and the Cu6Sn5 alloy's uneven shape becomes non-uniform, which increases the friction coefficient and reduces freight wear resistance. Furthermore, the radius of curvature of the convex portions becomes large, which increases the friction coefficient and tends to reduce freight wear resistance. The average KAM of the Cu6Sn5 alloy also becomes slightly lower.

[0051] The connector terminal material 1 thus formed has a coating 22 formed on a substrate 21 on which a plurality of terminal members 10 are successively formed, and the coating 22 includes a nickel layer 23 made of nickel or a nickel alloy, a copper-tin alloy layer 24 made of an alloy of copper and tin, and a tin layer 25 made of tin or a tin alloy, which are formed in this order. As described above, the coating 22 made of the nickel layer 23, the copper-tin alloy layer 24, and the tin layer 25 is formed not only on the front and back surfaces of the substrate 21 but also on both side surfaces, as well as on the front and back surfaces, so that the entire surface of the substrate 21 is covered with the coating 22. During the reflow treatment, the copper and tin in the copper plating layer 32 and the tin plating layer 33 react to form the copper-tin alloy layer 24 and the tin layer 25, but some of the copper in the copper plating layer 32 may remain unreacted, and a thin copper layer may exist between the nickel layer 23 and the copper-tin alloy layer 24.

[0052] In the case of a pin-shaped terminal using the terminal material 1 of this embodiment, as shown in Fig. 1, the connecting portion 13 that is connected to the mating terminal is formed in a long, thin pin shape, so that not only the front and back surfaces but also the side surfaces of the terminal material 1 may come into contact with the mating terminal, but even in this case, the performance as a connector is not impaired because the coating 22 is formed on the entire front, back, and side surfaces of the connecting portion 13. In addition, because the coating 22 is formed on the entire surface, corrosion is less likely to occur.

[0053] Furthermore, since the coating 22 has the nickel layer 23 formed thereon to cover the substrate 21, it is possible to prevent the diffusion of components such as copper (substrate components) from the substrate at high temperatures, thereby improving heat resistance. In addition, the copper-tin alloy layer 24 and the tin layer 25 have a composite structure in which the relatively soft tin layer 25 on the surface is supported by the hard copper-tin alloy layer 24, and the interface between them has an uneven shape, which, combined with the lubricating effect of the tin layer 25, can reduce the coefficient of friction.

[0054] In addition, in the copper-tin alloy layer 24, the average KAM of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate 21 is set in an appropriate range of 0.55° to 0.80°, so the copper-tin alloy layer is less likely to deform, wear of the copper-tin alloy layer during sliding is reduced, and freight wear resistance is improved. Furthermore, since the average thickness of the convex portions of the Cu6Sn5 alloy is 0.80 μm to 3.00 μm, the thickness of the copper-tin alloy layer is appropriate, the uneven shape is uniform, the friction coefficient is reduced, and freight wear resistance is improved. In the copper-tin alloy layer 24, the radius of curvature of the convex surface of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate 21 is 0.40 μm or more and 2.00 μm or less, which improves the sliding between the copper-tin alloy layers when sliding as a connector, and effectively demonstrates the function of the tin layer as a lubricant, resulting in a low friction coefficient and even better resistance to fretting wear.

[0055] In addition, the detailed configuration is not limited to that of the embodiment, and various modifications can be made within the scope that does not deviate from the spirit of the present invention. In the terminal material for connector 1 of the embodiment, the coating 22 is formed on the entire surface of the substrate 21, but it is sufficient that it is formed at least on the connection portion 13. In this connection portion 13, the coating 22 does not have to be formed on the entire surface of both the front and back sides, but only needs to be formed on the portion that comes into contact with the mating member. Furthermore, the substrate fixing part 14 may have a tin surface layer made of tin or a tin alloy formed on the entire surface (front, back and both side surfaces) instead of the coating 22. This tin surface layer may be the tin layer 25 described above, or may be a tin plating layer made of tin or a tin alloy formed on the base material 21 and then subjected to a reflow treatment. [Example]

[0056] The substrate was a 0.25mm thick sheet of CDA (Copper Development Association) alloy C18665. After punching out the terminal chain shape shown in the figure, electrolytic degreasing was performed as a pretreatment, and the surface was subsequently plated with nickel, copper, and tin. Furthermore, pickling was performed between each plating and after the copper plating. The conditions for electrolytic degreasing, pickling, and plating are listed in the order of the steps in Table 1, and the thickness of each plating layer was controlled by adjusting the plating time within the following ranges. Nickel plating: 15 seconds to 115 seconds Copper plating: 10 seconds to 80 seconds Tin plating: 15 seconds to 60 seconds In the following Examples and Comparative Examples, the same conditions were used except for the plating time. In the table, RT stands for room temperature.

[0057] [Table 1]

[0058] The substrates with plated layers thus formed were subjected to a reflow treatment. The reflow conditions are shown in Table 2. The reflow treatment was performed in an air atmosphere. In Comparative Example 11, the second heat treatment was not performed, and the substrate was cooled immediately after the first heat treatment.

[0059] [Table 2]

[0060] For the terminal material after reflow treatment, the average thickness of each layer of the coating, the average thickness of the convex part of the Cu6Sn5 alloy, the average KAM of the Cu6Sn5 alloy, the radius of curvature of the convex part surface of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate, the friction coefficient, and the contact resistance after heating were measured, and the fretting wear resistance was also evaluated.

[0061] (average thickness of each layer) When measuring the average thickness of each layer, the measurement area was part A in Figure 1. Part A is the center of the width direction at a position L1 = 2 mm (2 mm from the top edge of the paper in Figure 1) from the tip of the pin with a total length L0 = 28.8 mm, which corresponds to the connection part of the terminal. The thickness of the tin layer and the nickel layer was measured using a fluorescent X-ray film thickness meter (FT150) manufactured by Hitachi High-Tech Science Corporation. The nickel layer was left as it was, and the thickness of the tin-containing layer (the layer containing tin: the entire tin layer and copper-tin alloy layer) of the sample after reflow treatment was measured with a fluorescent X-ray thickness meter, and then the tin layer was removed by immersing the sample for several minutes in an etching solution for stripping tin plating films, such as L80 manufactured by Leybold Co., Ltd., which contains ingredients that etch tin but do not corrode copper-tin alloys, and the thickness of the tin-containing layer after etching was similarly measured with the fluorescent X-ray thickness meter. The thickness of the tin-containing layer after etching was then subtracted from the thickness of the tin-containing layer before etching to obtain the average thickness of the tin layer.

[0062] Regarding the average thickness of the copper-tin alloy layer, each sample was cross-sectionally processed using a focused ion beam device (FIB) (model number: SMI3050TB) manufactured by Seiko Instruments Inc., and the cross section thus formed was observed with a scanning ion microscope (SIM). In the cross-sectional SIM image at an inclination angle of 60°, the distance a from the interface with the nickel layer to the apex of the peak (protrusion) of the copper-tin alloy layer, and the distance b from the interface with the nickel layer to the valley of the copper-tin alloy layer were measured at 10 arbitrary locations each, and the average of these values ​​was calculated and then converted into an actual length to obtain the average thickness of the copper-tin alloy layer.

[0063] (Average thickness of the Cu6Sn5 alloy protrusions, and radius of curvature of the protrusion surface) The image processing software Image J (ver. 1.54f) was used to calculate the thickness of the Cu6Sn5 alloy protrusions and the radius of curvature of the surface of the protrusions. The thickness of the Cu6Sn5 alloy protrusions was determined by obtaining the thickness of 50 Cu6Sn5 alloy protrusions from cross-sectional SIM images parallel to the rolling direction of the substrate and averaging these values. In this case, the thickness was measured at the thickest point in the horizontal direction of the cross-sectional SIM image. The radius of curvature of the convex surface was determined by obtaining the radius of curvature for 10 convex portions from a cross-sectional SIM image parallel to the rolling direction of the substrate, and then calculating the average value. In this case, the curvature was obtained using "Kappa," a curvature calculation function in the image processing software Image J, and calculated by taking the reciprocal of the curvature. In "Kappa," the Curve Input Type was set to B-Spline and the B-Spline Type was set to Closed. The curvature of the convex surface of each Cu6Sn5 alloy was determined by tracing the contours from convex portion to convex portion of the Cu6Sn5 alloy to fit the convex shape of the Cu6Sn5 alloy from the cross section to an ellipse, and then obtaining the value at the highest point of one of the convex portions of the Cu6Sn5 alloy.

[0064] (Average KAM of Cu6Sn5 alloy) The crystal orientation was measured using electron backscatter diffraction to calculate the KAM (kernel average misorientation) of the Cu6Sn5 alloy. An EBSD measurement system (JEOL Ltd., scanning electron microscope JSM-7001FA, EDAX / TSL, OIM Data Collection) and analysis software (EDAX / TSL, OIM Data Analysis ver. 7.3) were used. The electron beam acceleration voltage of the EBSD measurement system was 15 kV, and the measurement area was 50 μm2, the cross-sectional area of ​​the Cu6Sn5. 2 The crystal orientation measurement step size was set to 0.02 μm. Data obtained from the EBSD measurement device was processed using analysis software, and measurement points where the difference in crystal orientation between adjacent measurement points was 5° or more were considered to be grain boundaries, and the average KAM value of the Cu6Sn5 alloy was measured. Note that the average KAM value of Cu6Sn5 alloy was not measured for those that did not meet the specified average thickness of the copper-tin alloy layer.

[0065] (coefficient of friction) Each sample was cut into a 60 mm long test piece parallel to the rolling direction of the substrate and used as a substitute for a male terminal (male terminal test piece). The female terminal test pieces were all the same. The unprocessed terminal-shaped sample of Example 12 (base material: C18665 with a thickness of 0.25 mm) was cut into a 60 mm x 10 mm piece and embossed with a 1.5 mm radius at the center of the test piece. Measurements were performed using a Bruker AXS friction and wear tester (UMT-Tribolab). The convex surface of the female terminal test piece was placed horizontally, 5 mm below part A in Figure 1, so that part A was the center of the sliding area. While applying a load of 2 to the male terminal test piece, the test piece was slid 10 mm to a position 5 mm above part A in Figure 1. Friction coefficient data was obtained every 0.013 mm of sliding distance, and the average value of the friction coefficient obtained between sliding distances of 0.1 mm and 10 mm was taken as the friction coefficient value.

[0066] (contact resistance) Test pieces were prepared in the same way as for the coefficient of friction, and after heating them at 150°C for 250 hours, the contact resistance (mΩ) of each was measured. A friction and wear tester (UMT-Tribolab) manufactured by Bruker AXS was used to measure the contact resistance when the convex surface of the female test piece was brought into contact with the horizontally placed male terminal test piece and a load of 5 N was applied to the male terminal test piece, using the four-terminal method.

[0067] (fretting wear resistance) Test specimens were prepared in the same manner as for measuring the friction coefficient and contact resistance, and fretting wear resistance was evaluated. A Bruker AXS friction and wear tester (UMT-Tribolab) was used to measure the fretting wear resistance. The convex surface of the female test specimen was placed in contact with part A (Figure 1) of the horizontally placed male terminal test specimen. A load of 2 N was applied to the male terminal test specimen, and the specimen was slid back and forth over a distance of 1 mm. The sliding speed was 1.3 mm / s, and one sliding cycle was counted as the time when the convex surface of the female test specimen slid 1 mm from part A to its return to part A. The fretting wear resistance was assessed by the number of cycles at which the substrate was exposed. A was assigned to specimens that did not expose the substrate even after 100 or more cycles; B was assigned to specimens that exposed the substrate after 25 to 99 cycles; and C was assigned to specimens that exposed the substrate after fewer than 25 cycles.

[0068] The results of these measurements are shown in Table 3. Items that were not measured or evaluated are marked with "-".

[0069] [Table 3]

[0070] Examples 1 to 14, in which the average thickness of the nickel layer was 0.30 μm or more and 3.00 μm or less, the average thickness of the copper-tin alloy layer was 0.30 μm or more and 1.20 μm or less, the average thickness of the tin layer was 0.15 μm or more and 0.80 μm or less, the average thickness of the convex portions of the Cu6Sn5 alloy in the copper-tin alloy layer was 0.80 μm or more and 3.00 μm or less, and the average KAM of the Cu6Sn5 alloy was 0.55° or more and 0.80° or less, had low friction coefficients and contact resistance after heating, and the fretting wear resistance was also good, with ratings of A and B.

[0071] FIG. 5 is a cross-sectional SIM image of Example 7, which shows that the interface between the copper-tin alloy layer and the tin layer is formed in a predetermined uneven shape.

[0072] On the other hand, in Comparative Examples 1 and 3, the copper-tin alloy layer was thin, so the average KAM of the Cu6Sn5 alloy, the thickness of the Cu6Sn5 alloy protrusions, and the radius of curvature of the protrusion surface were not measured. This is thought to be due to the insufficient first heat treatment. In contrast, in Comparative Example 2, the copper-tin alloy layer was thick, the average thickness of the Cu6Sn5 alloy projections was large, and the average KAM of the Cu6Sn5 alloy was also low. Therefore, the fretting wear resistance was low and the friction coefficient was high. Furthermore, because the tin layer was thin, the contact resistance after heating was high. This is thought to be due to the excessive first heat treatment. In Comparative Example 4, the average thickness of the Cu6Sn5 alloy projections was small, and in Comparative Example 8, the average thickness of the Cu6Sn5 alloy projections was small, both of which were poor in fretting wear resistance. This is thought to be due to an insufficient second heat treatment. On the other hand, in Comparative Examples 5 and 10, the average thickness of the Cu6Sn5 alloy projections was large, and both of which were poor in fretting wear resistance. This is thought to be due to an excessive second heat treatment. In Comparative Example 6, the copper-tin alloy layer was thick and the tin layer was thin. The average thickness of the Cu6Sn5 alloy protrusions was large. This resulted in poor fretting wear resistance and high contact resistance after heating. This is thought to be due to the first heat treatment being excessive. Normally, the average thickness of the Cu6Sn5 alloy protrusions is adjusted by the second heat treatment, but in Comparative Example 6, the first heat treatment was excessive, so it is assumed that the second heat treatment was unable to fully adjust it. In Comparative Example 7, the nickel layer was thin, and therefore the contact resistance increased after heating. In Comparative Example 9, the tin layer was too thick, and therefore the coefficient of friction was high. In Comparative Example 11, the average KAM value of the Cu6Sn5 alloy was low, and the average thickness of the convex portion of the Cu6Sn5 alloy was small. Therefore, the fretting wear resistance was poor. This is thought to be due to the cooling without performing the second heat treatment. [Explanation of symbols]

[0073] 1. Connector terminal material 10 Terminal materials 11 Connecting member 13 Connection 14 Board fixing part 21 Base material 22 Membrane 23 Nickel layer 24 Copper-tin alloy layer 25 Tin layer 31 Nickel plating layer 32 Copper plating layer 33 Tin plating layer 35 Substrate with plating layer

Claims

1. A coating is formed on the surface of a substrate made of copper or a copper alloy, and the coating has a nickel layer made of nickel or a nickel alloy formed on the surface of the substrate, a copper-tin alloy layer made of an alloy of copper and tin formed on the nickel layer, and a tin layer made of tin or a tin alloy formed on the copper-tin alloy layer, wherein the nickel layer has an average thickness of 0.30 μm or more and 3.00 μm or less, the copper-tin alloy layer has an average thickness of 0.30 μm or more and 1.20 μm or less, and the tin layer has an average thickness of 0.15 μm or more and 0.80 μm or less, and the copper-tin alloy layer has a Cu layer in which the interface with the tin layer has an uneven shape. ６ Sn ５ The Cu alloy is present in a cross section parallel to the rolling direction of the substrate. ６ Sn ５ The average thickness of the projections of the alloy is 0.80 μm or more and 3.00 μm or less, and the Cu in a cross section parallel to the rolling direction ６ Sn ５ A connector terminal material, characterized in that the average KAM value of the alloy is 0.55° or more and 0.80° or less.

2. The Cu in a cross section parallel to the rolling direction of the substrate ６ Sn ５ 2. The terminal material for a connector according to claim 1, wherein the radius of curvature of the surface of the convex portion of the alloy is 0.40 μm or more and 2.00 μm or less.

3. 3. A terminal material for a connector according to claim 1, characterized in that it has a connection portion to be connected to a mating side and a substrate fixing portion to be fixed to a substrate, and the coating is formed at least on the connection portion.

4. 4. The terminal material for a connector according to claim 3, wherein the board fixing portion has a tin surface layer made of tin or a tin alloy formed on the entire surface, back surface and both side surfaces.

5. a plating layer forming step of laminating a nickel plating layer made of nickel or a nickel alloy, a copper plating layer made of copper or a copper alloy, and a tin plating layer made of tin or a tin alloy in this order on a surface of a substrate made of copper or a copper alloy to form a substrate with a plating layer; and a reflow treatment step of heating the substrate with the plating layer to perform a reflow treatment, The reflow treatment process includes a first heating treatment in which the base material with the plating layer is heated at a furnace temperature of 240°C to 380°C for 5 to 30 seconds to melt the tin plating layer, and a second heating treatment in which the base material with the plating layer is heated at a furnace temperature of 150°C to 235°C for 10 to 60 seconds after the first heating treatment, and by cooling after the second heating treatment, a coating is formed on the base material, the coating comprising: a nickel layer made of nickel or a nickel alloy having an average thickness of 0.30 μm to 3.00 μm; a copper-tin alloy layer made of an alloy of copper and tin having an average thickness of 0.30 μm to 1.20 μm; and a tin layer made of tin or a tin alloy having an average thickness of 0.15 μm to 0.80 μm, laminated in this order.

6. A method for manufacturing a terminal material for a connector as described in claim 5, characterized in that before the plating layer forming process, a punching process is included in which a metal plate is punched to form a terminal chain body in which a plurality of terminal members are formed at intervals in the longitudinal direction of the elongated connecting member.

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