Connector terminal material and method for manufacturing the same

Abstract

It can be applied to various copper-based substrates, suppressing void formation, reducing the coefficient of friction, and preventing film peeling under prolonged high-temperature conditions. [Solution] A film is formed on the surface of a substrate made of copper or a copper alloy, and the film 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 a copper and tin alloy formed on the nickel layer, and a tin layer made of tin or a tin alloy formed on the copper-tin alloy layer, 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, 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 value 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 terminal material for a connector having heat resistance and low insertion force, and a method for manufacturing the same.

Background Art

[0002] Conventionally, a connector used for connecting electrical wiring in automobiles, consumer devices, etc. is designed to be electrically connected by a contact piece provided on a female terminal and a male terminal inserted into the female terminal contacting with a predetermined contact pressure. It includes a terminal pair.

[0003] As such a connector (terminal), a terminal material in which a copper-tin alloy layer and a tin layer are formed on a base material by applying copper plating and tin plating on a base material made of copper or a copper alloy and performing a reflow process is known.

[0004] As such a terminal material having a copper-tin alloy layer and a tin layer, for example, in Patent Document 1, by controlling the roughness of the base material and controlling the exposed state of the copper-tin alloy layer from the tin layer, the insertion force is reduced. However, it is necessary to process in advance to control the roughness of the base material. Therefore, it is difficult to apply it to a terminal material that is manufactured by plating after punching a terminal with a complicated and small part shape.

[0005] Also, in Patent Document 2, by making the tin layer made of tin or a tin alloy on the copper-tin alloy layer very thin, the insertion force is reduced. However, there is a problem that the contact resistance increases in a high-temperature environment because the tin layer is thin.

[0006] Also, in Patent Document 3, a part of the copper-tin alloy is replaced with nickel (Ni) to make the copper-tin alloy have a steep uneven shape and leave a certain amount of the tin layer, thereby reducing the friction coefficient and preventing an increase in contact resistance in a high-temperature environment. However, since the copper-tin alloy layer is steep, there is a limit to reducing the friction coefficient.

[0007] On the other hand, when forming a film by applying multiple layers of plating, the components of each plating layer are likely to diffuse due to heating and voids are likely to occur. If many voids occur, the film peels off. Therefore, Patent Document 4 describes using a specific copper alloy plate and forming a copper-tin alloy layer on it to suppress metal diffusion due to heating between the alloy additive components 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 cannot be used with brass-based alloys commonly used in pin terminals, and furthermore, it was not possible to completely suppress the peeling of the coating due to prolonged heating. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2007-100220 [Patent Document 2] Japanese Patent Publication No. 2011-012320 [Patent Document 3] Japanese Patent Publication No. 2014-240520 [Patent Document 4] Japanese Patent Publication No. 2005-226097 [Overview of the project] [Problems that the invention aims to solve]

[0009] In these terminal materials, the soft tin layer on the surface is prone to adhesion during insertion and removal, resulting in high insertion force. Furthermore, the friction coefficient reduction effect achieved by forming a copper-tin alloy layer is still insufficient. In addition, there were problems with void formation during reflow processing and peeling of the coating under prolonged high-temperature conditions.

[0010] This invention has been made in view of these circumstances, and aims to be applicable to various copper-based substrates, suppress the generation of voids, reduce the coefficient of friction, and prevent the peeling of the coating under high-temperature conditions for extended periods. [Means for solving the problem]

[0011] The connector terminal material of the present invention has a film formed on the surface of a base material made of copper or a copper alloy, and the film comprises a nickel layer made of nickel or a nickel alloy formed on the surface of the base material, a copper-tin alloy layer made of a copper-tin alloy 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, 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 value of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the base material is 0.48° or more and 0.70° or less.

[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. While a thicker average nickel layer generally leads to higher heat resistance, a certain thickness is unnecessary, and any thickness beyond that can easily cause cracking during processing, so an upper limit of 3.00 μm was set. On the other hand, if the average thickness of the nickel layer is less than 0.15 μm, the barrier function against the substrate components becomes insufficient, and the contact resistance tends to increase in high-temperature environments.

[0013] Furthermore, the copper-tin alloy layer and the tin layer are a composite structure in which the relatively soft tin layer on the surface is supported by the hard copper-tin alloy layer. Because the interface has an uneven shape, the coefficient of friction can be reduced in combination with the lubricating effect of the tin layer. 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 is less than 0.1 μm, the contact resistance value increases under prolonged high-temperature conditions. Furthermore, the amount of strain in the copper-tin alloy layer decreases, resulting in a lower average GOS (Grain Orientation Spread) value and a higher coefficient of friction. Additionally, the number of voids increases, making the coating more prone to peeling under prolonged high-temperature conditions. 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 coefficient of friction increases because there is less of the hard copper-tin alloy layer.

[0014] When the average thickness of the tin layer exceeds 2.0 μm, adhesive wear becomes more likely, resulting in a higher coefficient of friction. Conversely, when the average thickness of the tin layer is less than 0.1 μm, contact resistance increases under prolonged high-temperature conditions.

[0015] Furthermore, the higher the average GOS value of the Cu6Sn5 alloy in the copper-tin alloy layer, the more discontinuous the crystal structure in EBSD (Electron Backscatter Diffraction) is, making the copper-tin alloy layer less prone to deformation. This reduces wear during sliding, resulting in a better coefficient of friction. However, it is difficult to manufacture terminal materials with a GOS exceeding 0.70°.

[0016] On the other hand, if the average GOS value is less than 0.48°, the strain decreases, making the copper-tin alloy layer more prone to deformation during sliding, resulting in a higher coefficient of friction. Void formation also becomes more likely. However, even if the average GOS value is within a good range, if the film thickness of each layer does not meet the requirements, the number of voids will increase.

[0017] In the connector terminal material of the present invention, it is preferable that the average value of the aspect ratio Str of the surface properties of the copper-tin alloy layer is 0.3 or more and 0.7 or less. The surface texture aspect ratio Str is an index representing the isotropy or anisotropy of the surface texture, and takes a result between 0 and 1. When the average value of Str is less than 0.3, the irregularities of the copper-tin alloy layer become smaller, increasing the contact area of ​​the copper-tin alloy layer during sliding, reducing the lubricating effect of the tin layer, and tending to increase the coefficient of friction. On the other hand, when the average value of Str exceeds 0.7, the irregularities of the copper-tin alloy layer become larger, decreasing the contact area of ​​the copper-tin alloy layer during sliding, and thus tending to increase the coefficient of friction.

[0018] The connector terminal material of the present invention has a connecting portion that is connected to the mating side and a substrate fixing portion that is fixed to a substrate, and it is preferable that the coating is formed on at least 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 surfaces of the front surface, back surface, and both side surfaces.

[0019] By forming the above-mentioned film at least on the connection portion, a terminal excellent in insertion and extraction properties can be obtained. Also, in a terminal material for a connector that requires fixing to a substrate, it is preferable to use a "post-plating method" in which a metal plate is punched and then plated. The above-mentioned film is formed at least on the connection portion connected to the mating side, and it is preferable that a tin surface layer whose surface is made of tin or a tin alloy is formed on the entire surface of at least the substrate fixing portion. In a pin-shaped terminal, by forming a tin surface layer whose surface is made of tin or a tin alloy on the entire surface of the substrate fixing portion, a terminal excellent in solderability can be obtained, and by forming the above-mentioned film on the connection portion with the mating side, a terminal excellent in insertion and extraction properties can be obtained.

[0020] The manufacturing method of the 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 the surface of a base material made of copper or a copper alloy to form a base material with a plating layer, and a reflow treatment step of heating the base material with a plating layer to perform a reflow treatment. The reflow treatment step includes a first heat treatment of heating the base material with a plating layer in a first heating furnace set at a furnace temperature of 100°C or higher and 200°C or lower in an air atmosphere for 10 seconds or longer and 25 seconds or shorter, a second heat treatment of heating the base material with a plating layer in a second heating furnace set at a furnace temperature of 235°C or higher and 300°C or lower for 10 seconds or longer and 40 seconds or shorter after the first heat treatment to dissolve the tin plating layer, and after the second heat treatment, heating the base material with a plating layer in a third heating furnace set at a furnace temperature of 50°C or higher and 200°C or lower for 10 seconds or longer and 50 seconds or shorter and then cooling it, thereby forming a film in which a nickel layer with an average thickness of 0.15 μm or more and 3.00 μm or less, a copper-tin alloy layer with an average thickness of 0.2 μm or more and 1.0 μm or less, and a tin layer with an average thickness of 0.1 μm or more and 2.0 μm or less are laminated in this order on the base material.

[0021] By performing the reflow process in three stages of heating under predetermined temperature conditions and then cooling, the aspect ratio Str of the surface properties of the copper-tin alloy layer and the average GOS of the Cu6Sn5 alloy can be controlled to a predetermined range. Although the plating layer changes during the reflow process, it is referred to as a plated substrate until the reflow process is completed.

[0022] If the furnace temperature or time of the first heat treatment falls below the lower limit, heating to the second heat treatment is insufficient, resulting in smaller irregularities in the shape of the copper-tin alloy layer, less strain in the copper-tin alloy layer, a lower average value of Str and GOS, a higher coefficient of friction, and a larger number of voids. If the furnace temperature or time of the first heat treatment exceeds the upper limit, heating to the second heat treatment is excessive, resulting in less residual tin layer, higher contact resistance under prolonged high-temperature conditions, larger irregularities in the shape of the copper-tin alloy layer, a higher average value of Str, and furthermore, the copper-tin alloy layer becoming too thick, resulting in less strain, a lower average value of GOS, and a higher coefficient of friction. Furthermore, the number of voids increases, making the coating more prone to peeling under prolonged high-temperature conditions.

[0023] If the furnace temperature or time during the second heat treatment is insufficient, the irregularities in the shape of the copper-tin alloy layer will be small, resulting in less strain, a lower average value of Str and GOS, and a higher coefficient of friction. Furthermore, the number of voids will also increase. If the furnace temperature during the second heat treatment is too high or the time is too long, the amount of residual tin layer will be small, increasing the contact resistance under prolonged high-temperature conditions, the irregularities in the shape of the copper-tin alloy layer will be large, the average value of Str will increase, the copper-tin alloy layer will be too thick with less strain, the average value of GOS will decrease, and the coefficient of friction will increase. Furthermore, the number of voids will also increase, making the coating more prone to peeling under prolonged high-temperature conditions.

[0024] If the furnace temperature or time during the third heat treatment is insufficient, the strain in the copper-tin alloy layer decreases, resulting in a lower average GOS value and a higher coefficient of friction. Furthermore, the number of voids increases, making the coating more prone to peeling under prolonged high-temperature conditions. If the furnace temperature during the third heat treatment is too high or the time is too long, the strain in the copper-tin alloy layer decreases, resulting in a lower average GOS value and a higher coefficient of friction. In addition, metal diffusion due to heating becomes uneven, generating many voids and making the coating more prone to peeling under prolonged high-temperature conditions.

[0025] In the method for manufacturing terminal material for connectors of the present invention, it is preferable to have a punching step before the plating layer formation step in which a metal plate is punched out to form a terminal chain in which a plurality of terminal members are formed at intervals along the length of an elongated connecting member.

[0026] Because the punching process precedes the plating layer formation process, a coating is formed not only on the front and back surfaces of the terminal component but also on the punched cut end surface (side surface), 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, since the diffusion of the substrate components is prevented by a nickel layer of a predetermined thickness, it can be applied to various copper-based substrates. By controlling the average thickness of the copper-tin alloy layer and controlling the average GOS value of the Cu6Sn5 alloy to a predetermined range, the generation of voids is suppressed. In addition, in combination with the effect of the tin layer of a predetermined thickness on top of this copper-tin alloy layer, the coefficient of friction is reduced, peeling in high-temperature environments is suppressed, and heat resistance is improved. [Brief explanation of the drawing]

[0028] [Figure 1] This is a plan view of a connector terminal material according to an embodiment of the present invention. [Figure 2] Figure 1 is a schematic cross-sectional view of a connector terminal material. [Figure 3] Figure 1 is a flowchart showing the manufacturing method for connector terminal materials. [Figure 4]Figure 2 is a schematic cross-sectional view showing a plated substrate for connector terminal material before the reflow process. [Modes for carrying out the invention]

[0029] Embodiments of the present invention will be described below with reference to the drawings.

[0030] [Composition of connector terminal materials] As shown in Figure 1, the connector terminal material 1 of this embodiment is a terminal chain formed by connecting multiple terminal members 10, each having the shape of a pin terminal, and is formed by punching out a long sheet of 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, along a direction perpendicular to the length of the connecting member 11. Each terminal member 10 has a pin-shaped connecting portion 13 and a substrate fixing portion 14 that is narrower than the connecting portion 13, formed continuously from the tip, with the base end of the substrate fixing portion 14 connected to the connecting member 11 at a right angle. After being detached from the connecting member 11, the terminal member 10 is used in an electrically connected state to a substrate by press-fitting or soldering the substrate fixing portion 14 into a through-hole or the like of the substrate, and an electrical connection is made by inserting the connecting portion 13 into another female terminal. Note that the shape of the terminal component 10 is just an example and is not limited to the one shown in Figure 1; it can be any component that has a connecting portion for electrical connection with the mating terminal.

[0031] As schematically shown in Figure 2, the connector terminal material 1 has a coating 22 formed on a base material 21 made of copper or a copper alloy. The coating 22 consists of a nickel layer 23 made of nickel or a nickel alloy, a copper-tin alloy layer 24 made of a copper-tin alloy, and a tin layer 25 made of tin or a tin alloy, in that order. This tin layer 25 constitutes the surface layer of the coating 22. Figure 2 shows a cross-section, where the coating 22 is formed on the entire surface of both the front and back surfaces and both sides of the substrate 21.

[0032] The base material 21 is not particularly limited in composition as long as it is made of copper or a copper alloy, and is 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 to 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 under high-temperature conditions for a long period of time, increasing the contact resistance and potentially reducing heat resistance. While a larger average thickness of the nickel layer 23 improves heat resistance, a certain thickness is sufficient and nothing more is needed. If the average thickness of the nickel layer 23 exceeds 3.00 μm, cracking 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 process. It is formed from either only Cu6Sn5 alloy or a composite structure of most Cu6Sn5 alloy and some Cu3Sn alloy placed underneath. The surface of this copper-tin alloy layer 24, that is, the interface with the tin layer 25 above it, is formed in an uneven shape, and a portion of it is exposed on the surface of the tin layer 25.

[0035] The average thickness of the copper-tin alloy layer 24 is 0.2 μm or more and 1.0 μm or less. Furthermore, the average GOS value of the Cu6Sn5 alloy in the copper-tin alloy layer 24 in a cross section parallel to the rolling direction of the base material is 0.48° or more and 0.70° or less. In addition, it is preferable that the average aspect ratio Str of the surface properties 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 GOS value of the Cu6Sn5 alloy in the copper-tin alloy layer 24 are affected by the reflow treatment conditions described later and the thickness of the tin plating layer 33 and 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 is more than 2.0 μm due to insufficient heating during the reflow process, the coefficient of friction will increase because there will be less of the hard copper-tin alloy layer 24. If the average thickness of the tin layer 25 is less than 0.1 μm, the contact resistance will increase under prolonged high-temperature conditions, and the amount of strain in the copper-tin alloy layer 24 will decrease, lowering the average GOS value and increasing the coefficient of friction. Furthermore, the number of voids will increase, making the coating more prone to peeling under prolonged high-temperature conditions. The average thickness of this copper-tin alloy layer 24 is preferably 0.29 μm or more and 0.78 μm or less.

[0037] The average GOS value of Cu6Sn5 alloy is one of the orientation difference parameters obtained by EBSD (Electron Backscatter Diffraction) crystal orientation analysis, which is the average of the orientation difference between an arbitrary point and other points within the same crystal grain. It serves as an indicator of the magnitude of strain. The higher the GOS value, the more places there are discontinuities in the crystal structure as seen in EBSD, making the copper-tin alloy layer 24 less prone to deformation. This reduces wear during sliding, resulting in a better coefficient of friction. However, it is difficult to manufacture terminal materials with an orientation exceeding 0.70°. On the other hand, if the average GOS value is less than 0.48°, the strain decreases, making the copper-tin alloy layer 24 more prone to deformation during sliding, resulting in a higher coefficient of friction. Furthermore, under manufacturing conditions (plating formation conditions, reflow treatment conditions) where the average GOS value is less than 0.48°, metal diffusion due to heating becomes uneven, leading to the generation of many voids and the problem of film delamination under prolonged high-temperature conditions. Under manufacturing conditions that result in a good average GOS value, there are fewer voids, and film delamination under prolonged high-temperature conditions is suppressed. The average GOS value for this Cu6Sn5 alloy is preferably between 0.52° and 0.7°.

[0038] The aspect ratio Str of the surface properties of a copper-tin alloy layer is an index representing the isotropy or anisotropy of the surface properties, and takes a result between 0 and 1. If the average value of Str is less than 0.3, the irregularities of the copper-tin alloy layer 24 become smaller, increasing the contact area of ​​the copper-tin alloy layer 24 during sliding, reducing the effect of the tin layer 25 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 irregularities of the copper-tin alloy layer 24 become larger, decreasing the contact area of ​​the copper-tin alloy layer 24 during sliding, and thus tending to increase the coefficient of friction.

[0039] The tin layer 25 is a layer made of tin or a tin alloy, and its average thickness is formed to be between 0.1 μm and 2.0 μm. If the average thickness of this tin layer 25 exceeds 2.0 μm, adhesive wear is more likely to occur, resulting in a higher coefficient of friction. Conversely, if the average thickness of the tin layer 25 is less than 0.1 μm, the contact resistance increases under high-temperature conditions for extended periods. The average thickness of this tin layer 25 is preferably between 0.16 μm and 0.5 μm.

[0040] [Manufacturing method for connector terminal materials] Next, we will explain how to manufacture the terminal material 1 for this connector. The manufacturing method for this connector terminal material 1 includes a punching step in which a long, narrow metal plate is punched out by a press to form a terminal chain that will become a base material 21; a pre-treatment step in which the surface of the base material 21 after punching is cleaned; a plating layer formation step in which a nickel plating layer 31, a copper plating layer 32, and a tin plating layer 33 are sequentially formed on the surface of the base material 21; and a reflow treatment step in which the plated base material 35 with the three plating layers 31 to 33 is heated and reflow treated (see Figure 3). The process will be described below in order.

[0041] (punching process) A long, narrow metal plate made of copper or a copper alloy, wound into a coil, is fed out and punched out by a press to form a terminal chain that will become the base material 21 as shown in Figure 1.

[0042] (Pre-treatment process) The base material 21 after punching is subjected to a pre-treatment to clean the surface by degreasing, pickling, etc.

[0043] (Plating layer formation process) On the pre-treated substrate 21, 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 as follows (see Figure 4).

[0044] -Nickel plating layer- A nickel plating treatment is performed on the surface of a pre-treated substrate 21 to form a nickel plating layer 31 made of nickel or a nickel alloy. A general nickel plating bath can be used; for example, a sulfamic acid bath mainly composed of nickel sulfamate and boric acid can be used. The temperature of the plating bath is 50°C to 60°C, and the current density is 1 A / dm². 2 More than 10A / dm 2 The following is specified: The thickness of this nickel plating layer 31 is specified to be between 0.15 μm and 3.0 μm.

[0045] -Copper plating layer- A copper plating treatment is performed to form a copper plating layer 32 made of copper or a copper alloy on the nickel plating layer 31. A general copper plating bath can be used for the copper plating; for example, a copper sulfate bath mainly composed of copper sulfate and sulfuric acid can be used. The plating bath temperature should be between 20°C and 50°C, and the current density should be 1 A / dm². 2 More than 10A / dm 2 The following is specified: The thickness of this copper plating layer 32 is specified to be between 0.1 μm and 0.7 μm.

[0046] -Tin plating layer- A tin plating treatment is performed to form a tin plating layer 33 made of tin or a tin alloy on the copper plating layer 32. A general tin plating bath can be used as the plating bath for forming the tin plating layer 33; for example, a methanesulfonic acid bath mainly composed of methanesulfonic acid and tin methanesulfonate can be used. The plating bath temperature is 20°C to 40°C, and the current density is 1 A / dm².2 More than 20A / dm 2 The following is specified: The thickness of this tin plating layer 33 is specified to be between 0.4 μm and 3.0 μm.

[0047] In this manner, 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 plated substrate 35 with three stacked plating layers 31 to 33. Between each plating process, a cleaning treatment using sulfuric acid or the like is performed. Before this plating process, the substrate 21 is punched out into a chain terminal body by a press. The substrate 21 is then immersed in a plating bath to form the plating layers 31 to 33. As a result, three plating layers 31 to 33 are formed not only on both the front and back surfaces of the substrate 21, but also on both sides (the cut ends 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 the plating bath.

[0048] (Reflow process) As described above, the plated substrate 35 with the plated layers 31-33 is subjected to reflow processing. In the case of a long, narrow sheet material (strand material) wound on a roll, this reflow processing is carried out by running the sheet material in the length direction and passing it through a reflow oven while continuously performing the above-mentioned pretreatment and plating process. However, in the case of the plated substrate 35 of this embodiment, it is a punched material that has been punched out in advance as a terminal chain of a predetermined length as shown in Figure 1 by a press. After the above-mentioned pretreatment and plating process is applied to this punched material, the plated substrate 35 is supplied to a relatively small reflow oven and subjected to reflow processing.

[0049] Specifically, the process includes a first heating treatment in which a plated substrate 35 is heated for 10 to 25 seconds in a first heating furnace with an internal temperature of 100°C to 200°C in an atmospheric environment; a second heating treatment in which the plated substrate 35 is passed through a second heating furnace set to an internal temperature of 235°C to 300°C for 10 to 40 seconds to dissolve the tin plating layer 33 on the surface of the plated substrate 35; a third heating treatment in which the substrate is passed through a third heating furnace set to an internal temperature of 50°C to 200°C for 10 to 50 seconds after the second heating treatment; and a cooling treatment thereafter.

[0050] In this reflow process, the tin plating layer 33 is heated to just below the melting temperature in the first heat treatment, then the tin plating layer 33 is reflowed and melted in the second heat treatment, and then maintained at a low temperature in the third heat treatment. This controls the average value of the aspect ratio Str of the surface shape of the copper-tin alloy layer 24 and the GOS of the Cu6Sn5 alloy, thereby suppressing the generation of voids.

[0051] In this case, if the furnace temperature in the first heat treatment is less than 100°C or the heating time is less than 10 seconds, the heating for the second heat treatment is insufficient, the irregularities in the shape of the copper-tin alloy layer 24 are small, the strain of the copper-tin alloy layer 24 is small, the average values ​​of Str and GOS are low, the coefficient of friction is high, and the number of voids is also large. On the other hand, if the furnace temperature in the first heat treatment exceeds 200°C or the heating time exceeds 25 seconds, the heating for the second heat treatment is excessive, the amount of residual tin layer 25 is small, the contact resistance in a high-temperature environment for a long time is high, the irregularities in the surface shape of the copper-tin alloy layer 24 become large, Str is high, and furthermore the copper-tin alloy layer 24 is too thick, the strain is small, the average value of GOS is low, and the coefficient of friction is high. Furthermore, the number of voids also increases, and the coating is more likely to peel off in a high-temperature environment for a long time.

[0052] Furthermore, in the second heat 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 will be insufficient, resulting in smaller irregularities in the shape of the copper-tin alloy layer 24, less strain, a lower average value of Str and GOS, and a higher coefficient of friction. In addition, the number of voids will also increase. On the other hand, if the furnace temperature in the second heat treatment exceeds 300°C or the heating time exceeds 40 seconds, it will be overheated, resulting in less residual tin layer, higher contact resistance under prolonged high-temperature conditions, larger irregularities in the shape of the copper-tin alloy layer 24, a higher average value of Str, and a copper-tin alloy layer 24 that is too thick, resulting in less strain, a lower average value of GOS, and a higher coefficient of friction. In addition, the number of voids will also increase, making the coating more prone to peeling under prolonged high-temperature conditions.

[0053] In the third heat treatment, if the furnace temperature is below 50°C or the heating time is less than 10 seconds, insufficient heating reduces the strain in the copper-tin alloy layer, resulting in a lower average GOS value and a higher coefficient of friction. Furthermore, the number of voids increases, making the coating more prone to peeling under prolonged high-temperature conditions. If the furnace temperature in the third heat treatment exceeds 200°C or the heating time exceeds 50 seconds, the strain in the copper-tin alloy layer 24 decreases, resulting in a lower average GOS value and a higher coefficient of friction. In addition, metal diffusion due to heating becomes uneven, generating many voids and making the coating more prone to peeling under prolonged high-temperature conditions.

[0054] The connector terminal material 1 formed in this manner has a coating 22 formed on a base material 21 on which a plurality of terminal members 10 are continuously formed. The coating 22 is formed in the following order: a nickel layer 23 made of nickel or a nickel alloy, a copper-tin alloy layer 24 made of a copper-tin alloy, and a tin layer 25 made of tin or a tin alloy. As described above, the coating 22 consisting of the nickel layer 23, copper-tin alloy layer 24, and tin layer 25 is formed not only on the front and back surfaces of the base material 21, but also on both sides in the same way as the front and back surfaces, so that the entire surface of the base material 21 is covered with the coating 22. During the reflow process, 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. However, 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 Figure 1, the connecting portion 13 that connects to the mating terminal is formed in an elongated pin shape. Therefore, not only the front and back surfaces of the terminal material 1 but also the sides may come into contact with the mating terminal. However, even in this case, since the coating 22 is formed on the entire surface of the front, back, and sides of the connecting portion 13, the performance as a connector is not impaired. Furthermore, because the coating 22 is formed on the entire surface, corrosion is less likely to occur.

[0056] Furthermore, since the coating 22 has a nickel layer 23 covering the substrate 21, it is possible to prevent the diffusion of copper and other components (substrate components) from the substrate at high temperatures, thereby improving heat resistance. Furthermore, the copper-tin alloy layer 24 and the tin layer 25 have a composite structure in which the relatively soft tin layer 25 is supported by the hard copper-tin alloy layer 24, and since the interface has an uneven shape, the coefficient of friction can be reduced in combination with the lubricating effect of the tin layer 25.

[0057] Furthermore, since the average GOS value of the Cu6Sn5 alloy in the copper-tin alloy layer 24 is set within an appropriate range of 0.48° to 0.70°, the copper-tin alloy layer 24 is less prone to deformation, less likely to wear down during sliding, has a good coefficient of friction, generates fewer voids, and suppresses peeling of the coating 22 under high-temperature conditions for extended periods. Since the average aspect ratio Str of the surface properties of the copper-tin alloy layer 24 is between 0.3 and 0.7, the unevenness of the copper-tin alloy layer 24 exposes the copper-tin alloy layer to the surface of the tin layer 25 over an appropriate area. The hard contact points created by these exposed copper-tin alloy layers 24, combined with the lubricating effect of the tin layer 25 between them, can reduce the coefficient of friction.

[0058] Furthermore, the detailed configuration is not limited to that of the embodiment, and various modifications can be made without departing from the spirit of the present invention. In the connector terminal material 1 of this embodiment, a coating 22 is formed on the entire surface of the base material 21, but it is sufficient if it is formed on at least the connection portion 13. Even in this connection portion 13, it is sufficient if the coating 22 is formed on the portion that comes into contact with the mating member, rather than on the entire surface of both the front and back surfaces and both sides. Furthermore, the substrate fixing portion 14 may not necessarily have this coating 22, but rather a tin surface layer made of tin or a tin alloy formed on its entire surface (front, back, and both sides). This tin surface layer may be the aforementioned tin layer 25, or it may be a tin plating layer made of tin or a tin alloy formed on the substrate 21 and then reflow-treated. [Examples]

[0059] A 0.25 mm thick CDA (Copper Development Association) alloy, symbol C18665, was used as the base material. After punching it into the terminal chain shape shown in the figure, electrolytic degreasing was performed as a pretreatment, and nickel plating, copper plating, and tin plating were applied sequentially to the surface. Pickling treatment was also performed between each plating and after the copper plating. The conditions for electrolytic degreasing, pickling, and plating are shown in Table 1 in the order of the process, 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 to 70 seconds Tin plating: 15 seconds to 150 seconds Note that the following examples and comparative examples were conducted under the same conditions except for the plating time. In the table, RT represents room temperature.

[0060] [Table 1]

[0061] The plated substrates, on which various plating layers were formed in this manner, were subjected to reflow treatment. The reflow conditions are shown in Table 2. Comparative Example 15 was cooled immediately after the second heat treatment without performing the third 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 coefficient of friction, the number of voids, and the contact resistance after heating were measured. In addition, the adhesion of the coating after prolonged heating was evaluated by a heat peel resistance test.

[0064] (Average thickness of each layer) For measuring the average thickness of each layer, the measurement area was designated as section A in Figure 1. Section A is the central part in the width direction, located at a position L1 = 2 mm (2 mm from the top edge of the paper in Figure 1) from the tip of the pin, which has a total length of L0 = 28.8 mm and corresponds to the terminal connection part. The thickness of the nickel layer was measured using a Hitachi High-Tech Science Corporation X-ray fluorescence film thickness gauge (FT150). To determine the average thickness of the tin layer, the thickness of the tin-containing layer (the entire tin layer and copper-tin alloy layer) of the reflow-treated sample was first measured using a Hitachi High-Tech Science Corporation X-ray fluorescence film thickness gauge (FT150). Then, the tin layer was removed by immersing the sample in an etching solution for several minutes, such as Leybold Corporation L80, which is made of components that etch tin but do not corrode the copper-tin alloy. The thickness of the remaining tin-containing layer (copper-tin alloy layer) was then measured using a Hitachi High-Tech Science Corporation X-ray fluorescence film thickness gauge (FT150). 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] To determine the average thickness of the copper-tin alloy layer, each sample was cross-sectionally prepared using a focused ion beam (FIB) system (model: SMI3050TB) manufactured by Seiko Instruments Inc. The formed cross-sections were observed with a scanning ion microscope (SIM). In the cross-sectional SIM image at a 60° inclination angle, the distance 'a' from the interface with the nickel layer to 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. The average of these measurements was then calculated and converted to the actual length to obtain the average thickness of the copper-tin alloy layer.

[0066] (Average GOS of Cu6Sn5 alloy) The longitudinal section (parallel to the rolling direction) of each sample, including the plating layer, was mechanically polished using waterproof abrasive paper and diamond abrasive grains. The measurement surface was then processed using an Ar ion section processing device (Hitachi High-Tech Corporation IM4000 ion milling device). For crystal orientation measurement using electron backscatter diffraction to calculate GOS (Grain Orientation Spread), an EBSD measuring device (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 measuring device was set to 15kV, the measurement area was defined as an area containing 50 Cu6Sn5 crystals, and the step size for crystal orientation measurement was 0.02μm. Data obtained from the EBSD measuring device was processed using analysis software. Measurement points with a difference in crystal orientation of 5° or more were considered grain boundaries, and the average GOS value was measured. Note that the average GOS value was not measured for samples that did not meet the predetermined average thickness of the copper-tin alloy layer.

[0067] (Average aspect ratio Str of the surface properties of the copper-tin alloy layer) The tin layer was removed by immersion in an etching solution (Raybolt) for stripping the tin layer, exposing the underlying copper-tin alloy layer. Then, using a KEYENCE VK-X200 laser microscope, with an objective lens of 150x (measurement field of view 96 μm × 72 μm), an S filter of 1 μm, and an L filter of 0.1 mm, the Str value was calculated from the average value of five measurements taken at a total of five points on section A in Figure 1.

[0068] (Coefficient of friction) Each sample was cut into a 60mm long test piece parallel to the rolling direction and used as a substitute for the male terminal (male terminal test piece). For the female terminal sample, all samples were the same, and the sample from Example 13 (base material: C18665 material with a plate thickness of 0.25mm) which had not been processed into a terminal shape was cut to 60mm x 10mm, and an embossed pattern with a radius of curvature of 3.0mm was made in the center of the test piece. For measurement, a friction and wear tester (UMT-Tribolab) from Bruker AXS Corporation was used. The male terminal test piece was set up horizontally, and the convex surface of the female terminal test piece was brought into contact with the male terminal test piece 5mm below point A in Figure 1, so that point A in Figure 1 was the center of the sliding part. A load of 5N was applied to the male terminal test piece, and it was slid 10mm to a position 5mm above point A in Figure 1. Friction coefficient data was acquired at every 0.013 mm sliding distance, and the average of the friction coefficients obtained between 0.1 mm and 10 mm sliding distances was used as the friction coefficient value.

[0069] (Number of voids) Based on the aforementioned SIM images, voids with a diameter of 0.1 μm or larger were considered within a range of 30 μm perpendicular to the film deposition direction and 15 μm horizontally. The presence or absence of voids was determined, and if voids were present, the number of voids was counted.

[0070] (Heat peel resistance test) The heat peel resistance test was conducted in accordance with JCBA T317:2016. Each sample was cut into 50 mm long test pieces parallel to the rolling direction and 10 mm long in a direction perpendicular to it. After bending each piece 180°, they were heated at 150°C for 1000 hours. After heating, the test pieces were bent back, and a test tape was attached to the outer part of the bent portion of the coating surface. The tape was instantly peeled off to check for adhesion of the coating beneath the adhesive surface to the tape. Samples with no adhesion to the tape were classified as "A", samples with less than 10% of the peeled coating adhering to the adhesive surface of the attached tape were classified as "B", and samples with more than 10% of the coating adhering to the adhesive surface of the tape, clearly indicating peeling, were classified as "C". "A" and "B" were considered pass, and "C" was considered fail.

[0071] (contact resistance) Similar to the friction coefficient test, test specimens were prepared and heated at 150°C for 250 hours. After heating, the contact resistance (mΩ) of each was measured. For the measurement, a friction and wear tester (UMT-Tribolab) from Bruker AXS Corporation was used. The convex surface of the female test specimen was brought into contact with the horizontally positioned male terminal test specimen, and the contact resistance value was measured using the four-terminal method when a load of 5N was applied to the male terminal test specimen.

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

[0073] [Table 3]

[0074] Examples 1-17, in which the nickel layer had an average thickness of 0.15 μm to 3.00 μm, the copper-tin alloy layer had an average thickness of 0.2 μm to 1.0 μm, the tin layer had an average thickness of 0.1 μm to 2.0 μm, and the average GOS value of the Cu6Sn5 alloy was 0.48° to 0.70°, showed low friction coefficients and contact resistance after heating, a small number of voids, and good evaluation in the heat peel resistance test. Among these, Examples 1-5 and 7-17, in which the average aspect ratio Str of the surface properties of the copper-tin alloy layer was 0.3 to 0.7, showed excellent results. Example 6, in which the average aspect ratio Str was a slightly high 0.72, had a slightly higher friction coefficient.

[0075] On the other hand, in Comparative Examples 1, 2, 4, and 6, the copper-tin alloy layer was thicker due to the thinner tin layer, and the average GOS value of the Cu6Sn5 alloy was low, resulting in high friction coefficient and post-heat contact resistance, a large number of voids, and inferior evaluation in the heat peel resistance test. This is thought to be due to excessive first heat treatment in the reflow process for Comparative Examples 1 and 2, and excessive second heat treatment for Comparative Examples 4 and 6. Comparative Examples 3 and 5 had low average GOS values ​​and high coefficients of friction. They also had a high number of voids. In all cases, this is thought to be due to insufficient first heat treatment during the reflow process. In Comparative Example 7, the average GOS value was not measured because the copper-tin alloy layer was too thin. This is thought to be due to insufficient second heat treatment in the reflow process.

[0076] Comparative Example 8 had a low average GOS value, resulting in a high coefficient of friction, a thin tin layer, high contact resistance after heating, a large number of voids, and poor performance in the heat peel resistance test. This is thought to be due to excessive third-stage heat treatment in the reflow process. Comparative Examples 9 and 10 had low average GOS values ​​and high friction coefficients. Many voids were also present. This is likely due to insufficient second heat treatment in the reflow process for Comparative Example 9, and insufficient third heat treatment for Comparative Example 10. Comparative Example 11 had a low average GOS value and a high coefficient of friction. Many voids were also present. It is believed that the third heat treatment in the reflow process was excessive. In Comparative Example 12, the tin layer was thick and the copper-tin alloy layer was thin, so the average GOS value was not measured. This is thought to be due to insufficient second heat treatment and excessive third heat treatment in the reflow process.

[0077] Comparative Example 13 had a low average GOS value and a high coefficient of friction. Many voids were also present. This is likely due to the low furnace temperature during the third heat treatment of the reflow process. Comparative Example 14 had a thin nickel layer, resulting in high contact resistance after heating, a large number of voids, and poor performance in the heat peel resistance test. Comparative Example 15 had a low average GOS value and a high coefficient of friction. This is thought to be due to cooling without performing the third heat treatment in the reflow process. [Explanation of Symbols]

[0078] 1. Terminal material for connectors 10 Terminal components 11 Connecting member 13 Connection part 14. Substrate fixing part 21 Base material 22 Coating 23 Nickel layer 24 Copper-tin alloy layer 25 Tin layer 31 Nickel plating layer 32 Copper plating layer 33 Tin plating layer 35 Plating-coated substrate

Claims

1. A film is formed on the surface of a substrate made of copper or a copper alloy, and the film comprises a nickel layer made of nickel or a nickel alloy formed on the surface of the substrate, a copper-tin alloy layer made of a copper and tin alloy 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 Cu is present in the copper-tin alloy layer. ６ Sn ５ Having an alloy, the Cu in a cross-section parallel to the rolling direction of the base material ６ Sn ５ A terminal material for connectors characterized in that the average GOS value of the alloy is 0.48° or more and 0.70° or less.

2. The connector terminal material according to claim 1, characterized in that the average value of the aspect ratio Str of the surface properties of the copper-tin alloy layer is 0.3 or more and 0.7 or less.

3. The connector terminal material according to claim 1 or 2, having a connecting portion that is connected to the other side and a substrate fixing portion that is fixed to the substrate, and characterized in that the coating is formed on at least the connecting portion.

4. The connector terminal material according to claim 3, characterized in that the substrate fixing portion has a tin surface layer made of tin or a tin alloy formed on its entire surface, back surface, and both sides.

5. The process includes a plating layer formation step of forming a plated substrate by 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 onto the surface of a substrate made of copper or a copper alloy, and a reflow treatment step of heating the plated substrate and performing a reflow treatment. The reflow process is characterized by comprising: a first heat treatment in which the plated substrate is heated in a first heating furnace set to an internal temperature of 100°C to 200°C in an atmospheric environment for a period of 10 seconds to 25 seconds; a second heat treatment in which, after the first heat treatment, the plated substrate is heated in a second heating furnace set to an internal temperature of 235°C to 300°C for a period of 10 seconds to 40 seconds to melt the tin plating layer; and after the second heat treatment, the plated substrate is heated in a third heating furnace set to an internal temperature of 50°C to 200°C for a period of 10 seconds to 50 seconds, and then cooled, thereby forming a coating on the substrate in which a nickel layer with an average thickness of 0.15 μm to 3.00 μm, a copper-tin alloy layer with an average thickness of 0.2 μm to 1.0 μm, and a tin layer with an average thickness of 0.1 μm to 2.0 μm are laminated in this order.

6. The method for manufacturing a connector terminal material according to claim 5, characterized in that, prior to the plating layer forming step, a punching step is taken to punch out a metal plate to form a terminal chain in which a plurality of terminal members are formed at intervals along the length of an elongated connecting member.

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