Connector terminal material and its manufacturing method

Abstract

It can be applied to various copper-based substrates, suppresses the generation of voids, reduces the coefficient of friction, and prevents the coating from peeling off under long-term high-temperature environments. [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 0.15 μm or more and 3.00 μm or less, the average thickness of the copper-tin alloy layer is 0.2 μm or more and 1.0 μm or less, and the average thickness of the tin layer is 0.1 μm or more and 2.0 μm or less, and the copper-tin alloy layer contains a Cu6Sn5 alloy, and the average GOS of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate is 0.48° or more and 0.70° or less.

Description

[Technical Field]

[0001] The present invention relates to a heat-resistant, low-insertion-force terminal material for a connector, and a method for manufacturing 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, a terminal material having such a copper-tin alloy layer and a tin layer is disclosed in which the roughness of the substrate is controlled to control the state of exposure of the copper-tin alloy layer from the tin layer, thereby reducing the insertion force. However, the substrate must be processed in advance to control the roughness, which makes it difficult to apply this method to terminal materials for small terminals with complex shapes that are manufactured by punching and then plating.

[0005] In addition, in Patent Document 2, 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 small.

[0006] Furthermore, in Patent Document 3, part of the copper-tin alloy is replaced with nickel (Ni), the copper-tin alloy is made to have a steep uneven shape, and a certain amount of the tin layer is left, thereby reducing the friction coefficient and preventing an increase in contact resistance in high-temperature environments; however, because the copper-tin alloy layer is steep, there is a limit to how much the friction coefficient can be reduced.

[0007] On the other hand, when a coating is formed by applying plating to multiple layers, the components of each plating layer tend to diffuse when heated, which can easily cause voids. If many voids occur, the coating will peel off. Therefore, in Patent Document 4, a specific copper alloy plate is used and a copper-tin alloy layer is formed thereon, thereby suppressing metal diffusion due to heating between the alloy additives of the copper alloy plate and the copper-tin alloy layer, thereby preventing the generation of numerous voids. However, the copper alloy plate is limited, and it cannot be used with brass-based alloys that are often used in pin terminals, and furthermore, peeling of the coating due to long-term heating cannot be completely suppressed. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-100220 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-012320 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-240520 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-226097 Summary of the Invention [Problem to be solved by the invention]

[0009] The soft tin layer on the surface of these terminal materials tends to adhere during insertion and removal, resulting in high insertion forces. Furthermore, the effect of reducing the friction coefficient by forming a copper-tin alloy layer is still insufficient. Furthermore, voids occur during the reflow process, and the coating peels off under prolonged high-temperature conditions.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a coating that can be applied to various copper-based substrates, suppresses the generation of voids, reduces the coefficient of friction, and prevents peeling of the coating under high-temperature conditions for long periods of time. [Means for solving the problem]

[0011] The connector terminal material 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, wherein the average thickness of the nickel layer is 0.15 μm to 3.00 μm, the average thickness of the copper-tin alloy layer is 0.2 μm to 1.0 μm, and the average thickness of the tin layer is 0.1 μm to 2.0 μm, and the copper-tin alloy layer contains a Cu6Sn5 alloy, and the average GOS of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate is 0.48° to 0.70°.

[0012] The nickel layer has a barrier function that prevents the diffusion of copper and other components (substrate components) from the substrate at high temperatures, thereby improving heat resistance. The thicker 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 0.15 μm, the barrier function against substrate components will be insufficient, and contact resistance will likely increase in high-temperature environments.

[0013] 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 1.0 μm and the average thickness of the tin layer remaining after reflow treatment is less than 0.1 μm, the contact resistance will increase in a long-term high-temperature environment, and the amount of strain in the copper-tin alloy layer will decrease, resulting in a lower average GOS (Grain Orientation Spread) and a higher coefficient of friction. Furthermore, the number of voids will increase, making the coating more susceptible to peeling in a long-term high-temperature environment. On the other hand, if the average thickness of the copper-tin alloy layer is less than 0.2 μm and the average thickness of the tin layer exceeds 2.0 μm, the hard copper-tin alloy layer will decrease, resulting in a higher coefficient of friction.

[0014] If the average thickness of the tin layer exceeds 2.0 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 0.1 μm, contact resistance will increase when placed in a high-temperature environment for long periods of time.

[0015] Furthermore, the higher the average GOS of the Cu6Sn5 alloy in the copper-tin alloy layer, the more discontinuities there are in the crystal structure of EBSD (Electron Backscatter Diffraction), making the copper-tin alloy layer less susceptible to deformation. This reduces the copper-tin alloy layer's abrasion resistance during sliding, resulting in a good coefficient of friction. However, it is difficult to manufacture terminal materials with a GOS of more than 0.70°.

[0016] On the other hand, if the average GOS is less than 0.48°, the strain is reduced and the copper-tin alloy layer is easily deformed during sliding, resulting in a high coefficient of friction and voids being more likely to occur. However, even if the average GOS value is within a favorable range, if the film thickness of each layer does not meet the conditions, the number of voids will increase.

[0017] In the terminal material for a connector of the present invention, it is preferable that the average aspect ratio Str of the surface texture of the copper-tin alloy layer is 0.3 or more and 0.7 or less. The aspect ratio Str of the surface texture is an index that indicates whether the surface texture is isotropic or anisotropic, and takes a value between 0 and 1. If the average value of Str is less than 0.3, the unevenness of the copper-tin alloy layer becomes small, increasing the contact area of ​​the copper-tin alloy layer during sliding, reducing the effect of the tin layer as a lubricant and tending to increase the coefficient of friction.On the other hand, if the average value of Str exceeds 0.7, the unevenness of the copper-tin alloy layer becomes large, reducing the contact area of ​​the copper-tin alloy layer during sliding, tending to increase the coefficient of friction.

[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 in a first heating furnace set to an internal temperature of 100°C to 200°C in an air atmosphere for a period of 10 to 25 seconds; a second heating treatment in which, after the first heating treatment, the base material with the plating layer is heated in a second heating furnace set to an internal temperature of 235°C to 300°C for a period of 10 to 40 seconds to melt the tin plating layer; and, after the second heating treatment, the base material with the plating layer is heated in a third heating furnace set to an internal temperature of 50°C to 200°C for a period of 10 to 50 seconds, and then cooled, thereby forming a coating on the base material, which is layered in this order: a nickel layer having an average thickness of 0.15 μm to 3.00 μm; a copper-tin alloy layer having an average thickness of 0.2 μm to 1.0 μm; and a tin layer having an average thickness of 0.1 μm to 2.0 μm.

[0021] By performing the reflow treatment process as a three-stage heating process under predetermined temperature conditions and then cooling, it is possible to control the aspect ratio Str of the surface texture of the copper-tin alloy layer and the average value of GOS of the Cu6Sn5 alloy within a predetermined range. 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 time of the first heating treatment is below the lower limit, the heating in the second heating treatment is insufficient, resulting in small irregularities in the shape of the copper-tin alloy layer, little distortion in the copper-tin alloy layer, low average values ​​of Str and GOS, a high coefficient of friction, and a large number of voids. If the furnace temperature or time of the first heating treatment is above the upper limit, the heating in the second heating treatment is excessive, resulting in a small amount of remaining tin layer, high contact resistance in a long-term high-temperature environment, large irregularities in the shape of the copper-tin alloy layer, a high average value of Str, and the copper-tin alloy layer is too thick, resulting in little distortion, a low average value of GOS, and a high coefficient of friction. Furthermore, the number of voids increases, making the coating more susceptible to peeling in a long-term high-temperature environment.

[0023] If the furnace temperature or time of the second heating treatment is insufficient, the unevenness of the shape of the copper-tin alloy layer will be small, the distortion will be small, the average values ​​of Str and GOS will be low, and the friction coefficient will be high. Furthermore, the number of voids will also increase. If the furnace temperature of the second heating treatment is too high or the time is too long, the remaining tin layer will be small, the contact resistance will be high under prolonged high-temperature conditions, the unevenness of the shape of the copper-tin alloy layer will be large, the average value of Str will be high, and the copper-tin alloy layer will be too thick, the distortion will be small, the average value of GOS will be low, and the friction coefficient will be high. Furthermore, the number of voids will also increase, making the coating more susceptible to peeling under prolonged high-temperature conditions.

[0024] If the furnace temperature or time of the third heating treatment is insufficient, the strain in the copper-tin alloy layer will be reduced, the average GOS will be lower, and the coefficient of friction will be higher. Furthermore, the number of voids will increase, making the coating more likely to peel off under prolonged high-temperature conditions. If the furnace temperature or time of the third heating treatment is too high, the strain in the copper-tin alloy layer will be reduced, the average GOS will be lower, and the coefficient of friction will be higher. Furthermore, metal diffusion due to heating will be uneven, creating many voids, making the coating more likely to peel off under prolonged high-temperature conditions.

[0025] 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 connecting member.

[0026] 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]

[0027] According to the present invention, the nickel layer of a predetermined thickness prevents diffusion of the base material components, making it applicable to various copper-based base materials. By controlling the average thickness of the copper-tin alloy layer and controlling the average value of the GOS of the Cu6Sn5 alloy within a predetermined range, the generation of voids is suppressed, and coupled with the action of a tin layer of a predetermined thickness on this copper-tin alloy layer, the coefficient of friction is reduced, peeling is suppressed in high-temperature environments, and heat resistance is improved. [Brief explanation of the drawings]

[0028] [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. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0030] [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 and formed continuously from its tip, and the base end of the board fixing portion 14 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 press-fitting or soldering the board fixing portion 14 into a through-hole or the like in the board, thereby securing it in an electrically connected state to the board or the like, 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.

[0031] 2, the connector terminal material 1 has a coating 22 formed on a substrate 21 made of copper or a copper alloy, 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. The tin layer 25 forms the surface layer of the coating 22. Although a cross section is shown in FIG. 2, the coating 22 is formed on the entire surface of both the front and rear surfaces and both side surfaces of the substrate 21.

[0032] 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.

[0033] The nickel layer 23 has the function of suppressing the diffusion of copper and other components (substrate components) 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 preferably 0.15 μm or more and 3.00 μm or less. If the average thickness of the nickel layer 23 is less than 0.15 μm, copper may diffuse from the substrate 21 in a high-temperature environment for a long period of time, increasing the contact resistance and potentially reducing heat 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.

[0034] 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.

[0035] The average thickness of this copper-tin alloy layer 24 is 0.2 μm or more and 1.0 μm or less. Furthermore, the average GOS of the Cu6Sn5 alloy in the copper-tin alloy layer 24 in a cross section parallel to the rolling direction of the substrate is 0.48° or more and 0.70° or less. Furthermore, it is preferable that the average aspect ratio Str of the surface texture of the copper-tin alloy layer is 0.3 or more and 0.7 or less.

[0036] The average thickness of the copper-tin alloy layer 24 and the average value of GOS of the Cu6Sn5 alloy of the copper-tin alloy layer 24 are affected by the reflow treatment conditions described below and the thicknesses of the tin plating layer 33 and the copper plating layer 32 during manufacturing. If the average thickness of the copper-tin alloy layer 24 is less than 0.2 μm and the average thickness of the tin layer 25 exceeds 2.0 μm due to insufficient heating during the reflow process, the hard copper-tin alloy layer 24 is reduced, resulting in a high friction coefficient. If the average thickness of the tin layer 25 is less than 0.1 μm, the contact resistance increases under long-term high-temperature conditions, and the amount of strain in the copper-tin alloy layer 24 decreases, resulting in a low average GOS and a high friction coefficient. Furthermore, the number of voids increases, making the coating more susceptible to peeling under long-term high-temperature conditions. The average thickness of the copper-tin alloy layer 24 is preferably 0.29 μm or more and 0.78 μm or less.

[0037] The average GOS of the Cu6Sn5 alloy is one of the misorientation parameters obtained by EBSD (Electron Backscatter Diffraction) crystal orientation analysis, which averages the misorientation between a given point and other points within the same crystal grain. It is an index of the magnitude of strain. The higher the GOS value, the more discontinuities in the EBSD (Electron Backscatter Diffraction) crystal structure are broken, making the copper-tin alloy layer 24 less likely to deform. This reduces wear during sliding and improves the friction coefficient. However, it is difficult to manufacture terminal materials with an GOS of more than 0.70°. On the other hand, if the average GOS is less than 0.48°, the distortion is reduced and the copper-tin alloy layer 24 is more likely to deform during sliding, resulting in a higher friction coefficient. Furthermore, under manufacturing conditions (plating conditions, reflow treatment conditions) that result in an average GOS of less than 0.48°, metal diffusion due to heating becomes uneven, and many voids are likely to occur, resulting in the problem of film peeling under prolonged high-temperature conditions. Under manufacturing conditions that result in a good average GOS, there are fewer voids, and film peeling under prolonged high-temperature conditions is suppressed. The average value of GOS of this Cu6Sn5 alloy is preferably 0.52° or more and 0.7° or less.

[0038] The aspect ratio Str of the surface texture of the copper-tin alloy layer is an index that indicates whether the surface texture is isotropic or anisotropic, and takes a value of 0 to 1. If the average value of Str is less than 0.3, the unevenness of the copper-tin alloy layer 24 becomes small, the contact area of ​​the copper-tin alloy layer 24 during sliding increases, the effect of the tin layer 25 as a lubricant decreases, and the friction coefficient tends to increase. On the other hand, if the average value of Str exceeds 0.7, the unevenness of the copper-tin alloy layer 24 becomes large, the contact area of ​​the copper-tin alloy layer 24 during sliding decreases, and the friction coefficient tends to increase.

[0039] The tin layer 25 is a layer made of tin or a tin alloy, and is formed with an average thickness of 0.1 μm or more and 2.0 μm or less. If the average thickness of the tin layer 25 exceeds 2.0 μm, adhesive wear is more likely to occur, resulting in a high coefficient of friction. Conversely, if the average thickness of the tin layer 25 is less than 0.1 μm, the contact resistance will be high in a high-temperature environment for a long period of time. The average thickness of the tin layer 25 is preferably 0.16 μm or more and 0.5 μm or less.

[0040] [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.

[0041] (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 substrate 21 as shown in FIG.

[0042] (Pretreatment process) After punching, the base material 21 is subjected to pre-treatment such as degreasing and pickling to clean the surface.

[0043] (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).

[0044] -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 thickness of the nickel plating layer 31 is set to 0.15 μm or more and 3.0 μm or less.

[0045] -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 thickness of the copper plating layer 32 is set to 0.1 μm or more and 0.7 μm or less.

[0046] -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 / dm2 More than 20A / dm 2 The thickness of the tin plating layer 33 is set to 0.4 μm or more and 3.0 μm or less.

[0047] 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.

[0048] (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.

[0049] Specifically, the process includes a first heating treatment in which the plated layer-formed substrate 35 is heated in an air atmosphere in a first heating furnace set at a furnace temperature of 100°C to 200°C for a period of 10 to 25 seconds; a second heating treatment in which the plated layer-formed substrate 35 is passed through a second heating furnace set at a furnace temperature of 235°C to 300°C for a period of 10 to 40 seconds to melt the tin plating layer 33 on the surface of the plated layer-formed substrate 35; and a third heating treatment in which the plated layer-formed substrate 35 is passed through a third heating furnace set at a furnace temperature of 50°C to 200°C for a period of 10 to 50 seconds, followed by a cooling treatment.

[0050] In this reflow treatment, the first heating step heats the tin plating layer 33 to a temperature just below the melting point, and then the second heating step reflows and melts the tin plating layer 33. The third heating step then holds the layer at a low temperature, thereby controlling the aspect ratio Str of the surface shape of the copper-tin alloy layer 24 and the average value of the GOS of the Cu6Sn5 alloy and suppressing the occurrence of voids.

[0051] In this case, if the furnace temperature in the first heating treatment is less than 100°C or the heating time is less than 10 seconds, the heating in the second heating treatment is insufficient, resulting in small irregularities in the shape of the copper-tin alloy layer 24, reduced strain in the copper-tin alloy layer 24, low average Str and GOS values, a high coefficient of friction, and a large number of voids. On the other hand, if the furnace temperature in the first heating treatment exceeds 200°C or the heating time exceeds 25 seconds, the heating in the second heating treatment is excessive, resulting in a small amount of remaining tin layer 25, high contact resistance under prolonged high-temperature conditions, large irregularities in the surface shape of the copper-tin alloy layer 24, a high Str, and the copper-tin alloy layer 24 is too thick, reducing strain, low average GOS values, and a high coefficient of friction. Furthermore, the number of voids increases, making the coating more susceptible to peeling under prolonged high-temperature conditions.

[0052] Furthermore, in the second heating treatment, if the furnace temperature is less than 235°C or the heating time is less than 10 seconds, the formation of the copper-tin alloy is insufficient, resulting in small irregularities in the shape of the copper-tin alloy layer 24, reduced strain, low average values ​​of Str and GOS, and a high coefficient of friction. Furthermore, the number of voids increases. On the other hand, if the furnace temperature in the second heating treatment exceeds 300°C or the heating time exceeds 40 seconds, overheating occurs, resulting in a small amount of remaining tin layer, high contact resistance in a long-term high-temperature environment, large irregularities in the shape of the copper-tin alloy layer 24, a high average value of Str, and the copper-tin alloy layer 24 is too thick, resulting in low strain, low average value of GOS, and a high coefficient of friction. Furthermore, the number of voids increases, making the coating more susceptible to peeling in a long-term high-temperature environment.

[0053] In the third heating treatment, if the furnace temperature is below 50°C or the heating time is less than 10 seconds, the copper-tin alloy layer will be underheated, resulting in less strain, a lower average GOS, and a higher coefficient of friction. Furthermore, the number of voids will increase, making the coating more susceptible to peeling under prolonged high-temperature conditions. If the furnace temperature in the third heating treatment exceeds 200°C or the heating time exceeds 50 seconds, the copper-tin alloy layer 24 will be underheated, resulting in less strain, a lower average GOS, and a higher coefficient of friction. Furthermore, metal diffusion due to heating will be uneven, resulting in the formation of many voids, making the coating more susceptible to peeling under prolonged high-temperature conditions.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] Furthermore, since the average GOS of the Cu6Sn5 alloy of the copper-tin alloy layer 24 is set within an appropriate range of 0.48° or more and 0.70° or less, the copper-tin alloy layer 24 is less likely to deform and wear during sliding, resulting in a good coefficient of friction, little generation of voids, and suppression of peeling of the coating 22 under long periods of high-temperature environments. Since the average aspect ratio Str of the surface texture of the copper-tin alloy layer 24 is 0.3 or more and 0.7 or less, the unevenness of the copper-tin alloy layer 24 causes the copper-tin alloy layer to be exposed on the surface of the tin layer 25 over an appropriate area, and the hard contact caused by the exposed part of the copper-tin alloy layer 24, combined with the effect of the tin layer 25 acting as a lubricant therebetween, can reduce the coefficient of friction.

[0058] 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]

[0059] 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: 25 seconds to 250 seconds Copper plating: 10 seconds to 70 seconds Tin plating: 15 seconds to 150 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.

[0060] [Table 1]

[0061] The substrates with plated layers thus formed were subjected to a reflow treatment. The reflow conditions are shown in Table 2. In Comparative Example 15, the third heat treatment was not performed, and the substrate was cooled immediately after the second heat treatment.

[0062] [Table 2]

[0063] For the terminal material after reflow treatment, the average thickness of each layer of the coating, the average GOS of the Cu6Sn5 alloy, the average aspect ratio Str of the surface properties of the copper-tin alloy layer, the friction coefficient, the number of voids, and the contact resistance after heating were measured, and the adhesion of the coating after long-term heating was evaluated using a heat-resistance peeling test.

[0064] (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 nickel layer was measured using a fluorescent X-ray film thickness meter (FT150) manufactured by Hitachi High-Tech Science Corporation. Regarding the average thickness of the tin layer, first, the thickness of the tin-containing layer (layer containing tin: the entire tin layer and copper-tin alloy layer) of the sample after reflow treatment was measured using a fluorescent X-ray thickness meter (FT150) manufactured by Hitachi High-Tech Science Corporation, 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 Corporation, which contains components that etch tin but do not corrode copper-tin alloys, and the thickness of the remaining tin-containing layer (copper-tin alloy layer) was measured using a fluorescent X-ray thickness meter (FT150) manufactured by Hitachi High-Tech Science Corporation. The average thickness of the tin layer was defined by subtracting the thickness of the tin-containing layer after etching from the thickness of the tin-containing layer before etching.

[0065] 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 peak of the peak 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.

[0066] (Average GOS of Cu6Sn5 alloy) The longitudinal cross section (surface parallel to the rolling direction) of each sample, including the plating layer, was mechanically polished using waterproof polishing paper and diamond abrasives. The measurement surface was then processed using an Ar ion cross-section processing device (Ion Milling System IM4000, Hitachi High-Tech Corporation). Crystal orientation measurements using electron backscatter diffraction (EBSD) were performed using a JEOL JSM-7001FA scanning electron microscope and EDAX / TSL OIM Data Collection software (EDAX / TSL OIM Data Analysis ver. 7.3). The EBSD measurement device's electron beam acceleration voltage was 15 kV, the measurement area included 50 Cu6Sn5 crystals, and the step size for crystal orientation measurements was 0.02 μm. The data obtained by the EBSD measurement device was processed using analysis software, and the average GOS was measured by regarding the difference in crystal orientation between adjacent measurement points of 5° or more as a grain boundary. Note that the average GOS was not measured for samples that did not meet the specified average thickness of the copper-tin alloy layer.

[0067] (Average aspect ratio Str of the surface texture of the copper-tin alloy layer) The tin layer was removed by immersion in an etching solution (Rayvolt) for stripping the tin layer, exposing the underlying copper-tin alloy layer. Using a laser microscope (VK-X200) manufactured by Keyence Corporation, the objective lens was set at 150x (measurement field of view 96 μm × 72 μm), the S filter was set at 1 μm, and the L filter was set at 0.1 mm. A total of five measurements were taken at part A in Figure 1, and the average Str was calculated.

[0068] (coefficient of friction) Each sample was cut into a 60 mm long test piece parallel to the rolling direction and used as a male terminal substitute (male terminal test piece). The female terminal test pieces were all the same. The unprocessed terminal-shaped sample of Example 13 (base material: 0.25 mm thick C18665) was cut into a 60 mm x 10 mm piece and embossed with a 3.0 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. A load of 5 N was applied to the male terminal test piece, and the female terminal 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.

[0069] (Number of voids) From the SIM images mentioned above, voids with a diameter of 0.1 μm or more within a range of 30 μm vertically and 15 μm horizontally relative to the film formation direction were considered to be voids, and the presence or absence of voids was determined. If voids were present, the number of voids was counted.

[0070] (heat resistance peeling test) The heat peel resistance test was conducted in accordance with JCBA T317:2016. Each sample was cut into 50 mm long specimens parallel to the rolling direction and 10 mm long specimens perpendicular to the rolling direction. They were bent 180° and then heated at 150°C for 1,000 hours. After heating, the specimens were unbent, and test tape was applied to the outer edge of the bent portion of the coating surface. The tape was then quickly peeled off to confirm adhesion of the coating under the adhesive surface to the tape. A rating of "A" was given for no adhesion to the tape; a rating of "B" was given for coating that adhered to less than 10% of the adhesive surface of the applied tape; and a rating of "C" was given for coating that adhered to more than 10% of the adhesive surface and showed obvious peeling. "A" and "B" were considered pass, and "C" was considered fail.

[0071] (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.

[0072] The results of these measurements are shown in Table 3. Items that were not measured or evaluated are marked with "-".

[0073] [Table 3]

[0074] Examples 1 to 17, in which the average thickness of the nickel layer was 0.15 μm to 3.00 μm, the average thickness of the copper-tin alloy layer was 0.2 μm to 1.0 μm, and the average thickness of the tin layer was 0.1 μm to 2.0 μm, and the average GOS of the Cu6Sn5 alloy was 0.48° to 0.70°, had low friction coefficients and post-heat contact resistance, few voids, and were evaluated favorably in the heat peel resistance test. Among these, Examples 1 to 5 and 7 to 17, in which the average aspect ratio Str of the surface texture of the copper-tin alloy layer was 0.3 to 0.7, achieved excellent results. Example 6, in which the average aspect ratio Str was 0.72, was slightly high, had a slightly higher friction coefficient.

[0075] On the other hand, in Comparative Examples 1, 2, 4, and 6, the tin layer was thin, but the copper-tin alloy layer was thick. In addition, the average GOS of the Cu6Sn5 alloy was low, the friction coefficient and post-heat contact resistance were high, the number of voids was large, and the evaluation in the heat peel resistance test was poor. This is thought to be due to the fact that the first heat treatment in the reflow treatment was excessive in Comparative Examples 1 and 2, and the second heat treatment in Comparative Examples 4 and 6. Comparative Examples 3 and 5 had low average GOS and high coefficients of friction. They also had a large number of voids. Both of these were thought to be due to the insufficient first heating treatment in the reflow treatment. In Comparative Example 7, the average value of GOS was not measured because the copper-tin alloy layer was thin, which is thought to be because the second heat treatment in the reflow treatment was insufficient.

[0076] In Comparative Example 8, the average GOS was low, resulting in a high coefficient of friction, a thin tin layer due to the low average GOS, high contact resistance after heating, a large number of voids, and a poor evaluation in the heat peel resistance test. This is thought to be due to excessive third heating treatment in the reflow process. Comparative Examples 9 and 10 had low average GOS and high coefficients of friction. Many voids also occurred. This is thought to be due to the second heat treatment of the reflow process being insufficient in Comparative Example 9, and the third heat treatment being insufficient in Comparative Example 10. Comparative Example 11 had a low average GOS and a high coefficient of friction. Numerous voids were also generated. This is thought to be due to excessive third heat treatment in the reflow treatment. In Comparative Example 12, the average GOS was not measured because the tin layer was thick and the copper-tin alloy layer was thin. This is thought to be because the second heating treatment in the reflow treatment was insufficient and the third heating treatment was excessive.

[0077] Comparative Example 13 had a low average GOS and a high coefficient of friction. Many voids also occurred. This is thought to be due to the low furnace temperature in the third heating step of the reflow process. In Comparative Example 14, the nickel layer was thin, so the contact resistance after heating was high, the number of voids was large, and the evaluation in the heat peel resistance test was also poor. Comparative Example 15 had a low average GOS and a high coefficient of friction, which is thought to be because cooling was performed without carrying out the third heat treatment of the reflow treatment. [Explanation of symbols]

[0078] 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 average thickness of the nickel layer is 0.15 μm or more and 3.00 μm or less, the average thickness of the copper-tin alloy layer is 0.2 μm or more and 1.0 μm or less, and the average thickness of the tin layer is 0.1 μm or more and 2.0 μm or less, and the copper-tin alloy layer does not contain Cu. ６ Sn ５ The Cu alloy is present in a cross section parallel to the rolling direction of the substrate. ６ Sn ５ A terminal material for connectors, characterized in that the average value of GOS of the alloy is 0.48° or more and 0.70° or less.

2. 2. The terminal material for a connector according to claim 1, wherein the average aspect ratio Str of the surface texture of the copper-tin alloy layer is 0.3 or more and 0.7 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 step includes a first heating treatment in which the base material with the plating layer is heated in a first heating furnace set to an internal temperature of 100°C to 200°C in an air atmosphere for a period of 10 to 25 seconds; a second heating treatment in which the base material with the plating layer is heated in a second heating furnace set to an internal temperature of 235°C to 300°C in the air atmosphere for a period of 10 to 40 seconds to melt the tin plating layer; and a third heating furnace set to an internal temperature of 50°C to 200°C in the air atmosphere for a period of 10 to 50 seconds, followed by cooling the base material with the plating layer. This method for manufacturing a connector terminal material is characterized in that a coating is formed on the base material, the coating comprising a nickel layer having an average thickness of 0.15 μm to 3.00 μm, a copper-tin alloy layer having an average thickness of 0.2 μm to 1.0 μm, and a tin layer having an average thickness of 0.1 μm to 2.0 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.

Images