Connector terminal material and method for manufacturing the same

Abstract

In addition to maintaining a low coefficient of friction, the aim is to improve resistance to micro-sliding wear. [Solution] A film is formed on the surface of a substrate made of copper or a copper alloy. 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-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 0.30 μm or more and 3.00 μm or less, the average thickness of the copper-tin alloy layer is 0.30 μm or more and 1.20 μm or less, and the average thickness of the tin layer is 0.15 μm or more and 0.80 μm or less. The copper-tin alloy layer contains a Cu6Sn5 alloy whose interface with the tin layer has an uneven shape. The average thickness of the protrusions of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate is 0.80 μm or more and 3.00 μm or less. The average KAM of the Cu6Sn5 alloy in a cross section parallel to the rolling direction is 0.55° or more and 0.80° or less.

Description

Technical Field

[0001] The present invention relates to a terminal material for a connector having resistance to micro-sliding wear 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, and includes a terminal pair.

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

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

[0005] Also, in Patent Document 2, a part of the copper-tin alloy is replaced with nickel to make the copper-tin alloy have a steep uneven shape and leave the tin layer, thereby reducing friction and preventing the contact resistance from increasing during heating. However, since the copper-tin alloy layer is steep, there is a limit to reducing the frictional force.

[0006] On the other hand, in Patent Document 3, instead of the copper-tin alloy layer, a nickel-tin alloy layer made of Ni3Sn4 is formed. However, since the alloy shape is elongated and the alloy containing nickel oxidizes, the resistance significantly increases, so the connection reliability and resistance to micro-sliding wear are insufficient.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

[0008] In these terminal materials, the soft tin layer on the surface tends to adhere during insertion and removal, resulting in high insertion force. Even when a hard alloy layer, such as a copper-tin alloy layer or a nickel-tin alloy layer, is formed beneath the tin layer, the shape has not been optimized, and there is still a problem of insufficient resistance to micro-sliding wear when used for connecting electrical wiring in automobiles and consumer electronics where micro-sliding occurs.

[0009] This invention has been made in view of these circumstances, and aims not only to maintain a low coefficient of friction but also to improve resistance to micro-sliding wear. [Means for solving the problem]

[0010] The connector terminal material of the present invention has a coating formed on the surface of a base material 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 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 0.30 μm or more and 3.00 μm or less, and the average thickness of the copper-tin alloy layer is 0.3 The copper-tin alloy layer has a thickness of 0 μm or more and 1.20 μm or less, an average thickness of the tin layer of 0.15 μm or more and 0.80 μm or less, and the copper-tin alloy layer contains a Cu6Sn5 alloy whose interface with the tin layer has an uneven shape, the average thickness of the protrusions of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate is 0.80 μm or more and 3.00 μm or less, and the average KAM of the Cu6Sn5 alloy in a cross section parallel to the rolling direction is 0.55° or more and 0.80° or less.

[0011] The nickel layer 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 greater the average thickness of this nickel layer, the higher the heat resistance, but beyond a certain thickness it is unnecessary, and since it is prone to cracking during processing, the upper limit was set at 3.00 μm. On the other hand, if the average thickness of the nickel layer is less than 0.30 μm, the barrier function against the substrate components is insufficient, and the contact resistance in high-temperature environments increases.

[0012] 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 1.20 μm, the uneven shape of the Cu6Sn5 alloy becomes non-uniform, the average value of the KAM (Kernel Average Misorientation) of the Cu6Sn5 alloy decreases, and the copper-tin alloy layer becomes less slippery during sliding, reducing its resistance to micro-sliding wear. On the other hand, if the average thickness of the copper-tin alloy layer is less than 0.30 μm, the coefficient of friction increases because there is less hard copper-tin alloy layer, and the resistance to micro-sliding wear decreases.

[0013] When the average thickness of the tin layer exceeds 0.80 μm, adhesive wear is more likely to occur, resulting in a higher coefficient of friction. Conversely, when the average thickness of the tin layer is less than 0.15 μm, there is less lubricating tin layer, which increases the coefficient of friction and thus the contact resistance in high-temperature environments.

[0014] Furthermore, a higher average KAM value for Cu6Sn5 alloy indicates that more small-angle grain boundaries with orientation differences of 5° or less are formed, making it less prone to deformation. This reduces wear of the copper-tin alloy layer during sliding and improves resistance to micro-sliding wear. However, because the stress is released during reflow, it is difficult to produce coatings with an angle exceeding 0.80°. On the other hand, if the average value of KAM is less than 0.55°, the strain decreases, making the copper-tin alloy layer more prone to deformation during sliding. This increases the coefficient of friction and reduces resistance to micro-sliding wear.

[0015] If the average thickness of the protrusions in the Cu6Sn5 alloy exceeds 3.00 μm, the average KAM value decreases, and the uneven shape of the Cu6Sn5 alloy becomes non-uniform, resulting in a higher coefficient of friction and reduced resistance to micro-sliding wear. If the average thickness of the protrusions is less than 0.80 μm, the thickness of the copper-tin alloy layer becomes thinner, the coefficient of friction increases, and the resistance to micro-sliding wear decreases.

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

[0017] When the radius of curvature of the convex surface of the Cu6Sn5 alloy exceeds 2.00 μm, the friction between the Cu6Sn5 alloys increases during sliding as a connector, reducing the effectiveness of the tin layer as a lubricant. This tends to increase the coefficient of friction and decrease resistance to micro-sliding wear. On the other hand, when the radius of curvature is less than 0.40 μm, the contact points between the Cu6Sn5 alloys during sliding as a connector are fewer and more uneven, increasing the coefficient of friction and decreasing resistance to micro-sliding wear.

[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, the substrate fixing portion may have a tin surface layer made of tin or a tin alloy formed on its entire surface, including the front, back, and both sides.

[0019] At least the aforementioned coating is formed on the connection portion, resulting in a terminal with excellent insertion and removal properties. Furthermore, for connector terminal materials that require fixing to a substrate, it is preferable to use a "post-plating method" in which a metal plate is plated after punching it out, and it is preferable that the aforementioned coating is formed at least on the connecting portion that is connected to the mating side, and that a tin surface layer made of tin or a tin alloy is formed over the entire surface of at least the portion that is fixed to the substrate. In a pin-shaped terminal, a tin surface layer whose surface is made of tin or a tin alloy is formed on the entire surface of the substrate fixing portion, thereby providing excellent solderability. In addition, by forming the above-mentioned film on the connection portion with the mating side, a terminal excellent in insertion and extraction properties is obtained.

[0020] The manufacturing method of the terminal material for a connector according to 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 at a furnace temperature of 240°C or higher and 380°C or lower for 5 seconds or longer and 30 seconds or shorter to dissolve the tin plating layer, and a second heat treatment of heating the base material with a plating layer at a furnace temperature of 150°C or higher and 235°C or lower for 10 seconds or longer and 60 seconds or shorter after the first heat treatment. By cooling after the second heat treatment, a film is formed on the base material by laminating a nickel layer made of nickel or a nickel alloy with an average thickness of 0.30 μm or more and 3.00 μm or less, a copper-tin alloy layer made of an alloy of copper and tin with an average thickness of 0.30 μm or more and 1.20 μm or less, and a tin layer made of tin or a tin alloy with an average thickness of 0.15 μm or more and 0.80 μm or less in this order.

[0021] By cooling the reflow treatment step as two-stage heating under predetermined temperature conditions, the average value of KAM of the Cu6Sn5 alloy, the average value of the thickness of the convex portion, and the radius of curvature of the convex portion surface in the above-mentioned copper-tin alloy layer can be controlled within a predetermined range. Although the plating layer changes during the reflow treatment step, it is referred to as a base material with a plating layer until the reflow treatment step is completed.

[0022] When the furnace temperature or heating time of the first heat treatment is below the lower limit, the growth of the copper-tin alloy layer becomes insufficient, the convex portions of the Cu6Sn5 alloy are also thin, the friction coefficient becomes high, and the resistance to micro-sliding wear decreases. If the furnace temperature or heating time during the first heat treatment exceeds the upper limit, the copper-tin alloy layer grows excessively, resulting in larger protrusions in the Cu6Sn5 alloy and an excessively thick copper-tin alloy layer. This leads to a thinner remaining tin layer, reducing the amount of lubricating tin, resulting in a higher coefficient of friction and increased contact resistance in high-temperature environments. Furthermore, the uneven shape of the Cu6Sn5 alloy becomes non-uniform, and the radius of curvature of the protrusions increases, making it more difficult for the copper-tin alloy layer to slide during sliding, thus reducing resistance to micro-sliding wear. The average KAM value of the Cu6Sn5 alloy also decreases slightly.

[0023] If the furnace temperature or heating time during the second heat treatment falls below the lower limit, the Cu6Sn5 alloy will not grow to a sufficient size, resulting in thinner protrusions on the Cu6Sn5 alloy, a thinner copper-tin alloy layer, a higher coefficient of friction, and reduced resistance to micro-sliding wear. Furthermore, because the Cu6Sn5 alloy has a pointed shape and a smaller radius of curvature, the coefficient of friction tends to increase slightly, further reducing resistance to micro-sliding wear. If the furnace temperature or heating time during the second heat treatment exceeds the upper limit, the growth of the copper-tin alloy becomes excessive, causing the protrusions of the Cu6Sn5 alloy to become too thick and the uneven shape of the Cu6Sn5 alloy to become non-uniform. This increases the coefficient of friction and reduces resistance to micro-sliding wear. Furthermore, the radius of curvature of the protrusions increases, which tends to increase the coefficient of friction and further reduce resistance to micro-sliding wear. The average KAM of the Cu6Sn5 alloy also tends to be slightly lower.

[0024] 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 carrier portion.

[0025] Because the stamping 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 stamped-out cut ends (sides), allowing the terminal to exhibit stable characteristics regardless of the orientation in which it is used. [Effects of the Invention]

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

[0027] [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. [Figure 5] This is a backscattered electron (BSE) image of the cross-section of Example 7. [Modes for carrying out the invention]

[0028] Embodiments of the present invention will be described below with reference to the drawings.

[0029] [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 along a direction perpendicular to the length of a predetermined elongated connecting member 11 on one side 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 15 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 15 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.

[0030] 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. Figure 2 shows a cross-section of the substrate 21 parallel to the rolling direction, and the coating 22 is formed on the entire surface of both the front and back surfaces and both sides of the substrate 21.

[0031] 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.

[0032] 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 0.30 μm or more and 3.00 μm or less. If the average thickness of the nickel layer 23 is less than 0.30 μm, copper will diffuse from the substrate 21 in a high-temperature environment, increasing the contact resistance. The greater the average thickness of the nickel layer 23, the higher the heat resistance, but 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.

[0033] The copper-tin alloy layer 24 is obtained by sequentially forming a copper plating layer and a tin plating layer on the nickel layer 23 and then performing a reflow 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. The average thickness of this copper-tin alloy layer 24 is 0.30 μm or more and 1.20 μm or less. Furthermore, for the Cu6Sn5 alloy in the copper-tin alloy layer 24, the average thickness of the protrusions in a cross section parallel to the rolling direction of the base material 21 is 0.80 μm or more and 3.00 μm or less, and the average KAM of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the base material 21 is 0.55° or more and 0.80° or less. In addition, the radius of curvature of the surface of the protrusions of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the base material 21 should be 0.40 μm or more and 2.00 μm or less.

[0034] The average thickness of the protrusions of the Cu6Sn5 alloy in this copper-tin alloy layer 24 and the average KAM value are affected by the reflow treatment conditions and the thickness of the copper-tin alloy layer 24, which will be described later. If the furnace temperature or heating time during the first heat treatment in the reflow process falls below the lower limit, the growth of the copper-tin alloy layer 24 becomes insufficient, the protrusions of the Cu6Sn5 alloy become thinner, the coefficient of friction increases, and the resistance to micro-sliding wear decreases. If the protrusions of the Cu6Sn5 alloy become thicker, the average thickness of the copper-tin alloy layer 24 becomes too large, the tin layer becomes relatively thinner, and the amount of lubricating tin layer decreases, resulting in a higher coefficient of friction and increased contact resistance in high-temperature environments. Furthermore, the uneven shape of the Cu6Sn5 alloy becomes non-uniform, and the radius of curvature of the protrusion surface decreases, making it difficult for the copper-tin alloy layer to slide during sliding, which tends to reduce the resistance to micro-sliding wear. The average value of KAM (Kernel Average Misorientation) of the Cu6Sn5 alloy also decreases slightly. If the furnace temperature or heating time during the second heat treatment in the reflow process falls below the lower limit, the Cu6Sn5 alloy will not grow to a sufficient size. This results in thinner protrusions on the Cu6Sn5 alloy, a thinner copper-tin alloy layer, a higher coefficient of friction, and reduced resistance to micro-sliding wear. Furthermore, the pointed shape of the Cu6Sn5 alloy and the resulting smaller radius of curvature further increase the coefficient of friction, leading to a tendency for reduced resistance to micro-sliding wear. If the furnace temperature or heating time during the second heat treatment exceeds the upper limit, the growth of the copper-tin alloy layer 24 becomes excessive, causing the protrusions of the Cu6Sn5 alloy to become too thick and the uneven shape of the Cu6Sn5 alloy to become non-uniform. This increases the coefficient of friction and reduces resistance to micro-sliding wear. Furthermore, the radius of curvature of the protrusions increases, which tends to increase the coefficient of friction and further reduce resistance to micro-sliding wear. The average value of the KAM of the Cu6Sn5 alloy also tends to be slightly lower. The furnace temperature during this second heat treatment is preferably between 170°C and 220°C.

[0035] If the average thickness of the protrusions of the Cu6Sn5 alloy in the copper-tin alloy layer exceeds 3.00 μm, the average KAM value of the Cu6Sn5 alloy decreases, resulting in an uneven surface shape of the Cu6Sn5 alloy, which increases the coefficient of friction and reduces resistance to micro-sliding wear. If the average thickness of the protrusions is less than 0.80 μm, the thickness of the copper-tin alloy layer decreases, further reducing resistance to micro-sliding wear. Furthermore, when the radius of curvature of the convex surface of the Cu6Sn5 alloy exceeds 2.00 μm, the friction between the copper-tin alloy layers increases during sliding as a connector, reducing the effectiveness of the tin layer as a lubricant. This tends to increase the coefficient of friction and decrease resistance to micro-sliding wear. On the other hand, when the radius of curvature is less than 0.40 μm, the contact points between the copper-tin alloy layers during sliding as a connector are fewer and more uneven, increasing the coefficient of friction and decreasing resistance to micro-sliding wear.

[0036] The average KAM (Kernel Average Misorientation) value of Cu6Sn5 alloy is measured using the EBSD (Electron Back Scattered Diffraction) method. It represents the average of the orientation differences between adjacent measurement points and indicates local changes in crystal orientation. A larger average KAM value indicates greater strain. In this Cu6Sn5 alloy, a higher average KAM value indicates that more small-angle grain boundaries with orientation differences of 5° or less are formed, making it less prone to deformation. This reduces wear of the copper-tin alloy layer during sliding and improves resistance to micro-sliding wear. However, because the stress is released due to reflow, it is difficult to produce coatings with an angle exceeding 0.80°. On the other hand, if the average KAM value of the Cu6Sn5 alloy is less than 0.55°, the strain decreases, making the copper-tin alloy layer more prone to deformation during sliding. This results in a higher coefficient of friction and reduced resistance to micro-sliding wear.

[0037] The tin layer 25 is a layer made of tin or a tin alloy, and its average thickness is formed to be between 0.15 μm and 0.80 μm. If the average thickness of this tin layer exceeds 0.80 μm, adhesive wear is more likely to occur, resulting in a higher coefficient of friction. Conversely, if the average thickness of the tin layer is less than 0.15 μm, there is less tin layer with lubricating effect, resulting in a higher coefficient of friction and increased contact resistance in high-temperature environments.

[0038] [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.

[0039] (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.

[0040] (Pre-treatment process) The base material 21 after punching is subjected to a pre-treatment to clean the surface by degreasing, pickling, etc.

[0041] (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).

[0042] -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 considered to be the case.

[0043] -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 considered to be the case.

[0044] -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 considered to be the case.

[0045] 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.

[0046] (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.

[0047] The reflow process includes a first heat treatment in which the plated substrate 35 is passed through a first heating furnace with an internal temperature of 240°C to 380°C for a period of 5 seconds to 30 seconds to heat it above the melting point of tin and melt the tin plating layer; and a second heat treatment in which the plated substrate 35 is passed through a second heating furnace with an internal temperature of 150°C to 235°C for a period of 10 seconds to 60 seconds, followed by cooling after the second heat treatment.

[0048] In this reflow process, the tin plating layer 33 is melted by heating to a high temperature in the first heat treatment, and then the temperature is kept below the melting point of tin to control the interface shape between the copper-tin alloy layer 24 and the tin layer 25. This controls the average value of the KAM of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate 21, the average thickness of the protrusions of the Cu6Sn5 alloy in a cross section parallel to the rolling direction of the substrate, and the radius of curvature of the protrusion surface to a predetermined range, thereby reducing the coefficient of friction.

[0049] In this case, during the first heat treatment, if the furnace temperature is less than 240°C or the heating time is less than 5 seconds, the heating is insufficient, the copper-tin alloy layer 24 does not grow sufficiently, the protrusions of the Cu6Sn5 alloy at the interface with the tin layer 25 become thinner, the coefficient of friction increases, and the resistance to micro-sliding wear decreases. On the other hand, if the furnace temperature exceeds 380°C or the heating time exceeds 30 seconds, the growth of the copper-tin alloy layer becomes excessive, the protrusions of the Cu6Sn5 alloy become thicker, the thickness of the copper-tin alloy layer becomes too large, the remaining tin layer becomes thinner, and the amount of tin with lubricating effect decreases, resulting in a higher coefficient of friction and increased contact resistance in high-temperature environments. Furthermore, the uneven shape of the Cu6Sn5 alloy becomes non-uniform, and the radius of curvature of the protrusions also increases, so the copper-tin alloy layer tends to slide less easily during sliding, and the resistance to micro-sliding wear decreases. The average KAM of the Cu6Sn5 alloy also becomes slightly lower.

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

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Furthermore, in the copper-tin alloy layer 24, the average value of the KAM of the Cu6Sn5 alloy in a cross-section parallel to the rolling direction of the base material 21 is set to an appropriate range of 0.55° to 0.80°, so the copper-tin alloy layer becomes less prone to deformation, reducing wear of the copper-tin alloy layer during sliding and improving resistance to micro-sliding wear. In addition, since the average thickness of the protrusions of the Cu6Sn5 alloy is between 0.80 μm and 3.00 μm, the thickness of the copper-tin alloy layer becomes appropriate, its uneven shape becomes uniform, the coefficient of friction is reduced, and resistance to micro-sliding wear is improved. In the copper-tin alloy layer 24, the radius of curvature of the convex surface of the Cu6Sn5 alloy in a cross-section parallel to the rolling direction of the base material 21 is between 0.40 μm and 2.00 μm. This ensures good sliding between the copper-tin alloy layers during sliding as a connector, and allows the tin layer to effectively function as a lubricant, resulting in a low coefficient of friction and even better resistance to micro-sliding wear.

[0055] 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]

[0056] 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: 15 seconds to 115 seconds Copper plating: 10 to 80 seconds Tin plating: 15 seconds to 60 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.

[0057] [Table 1]

[0058] The plated substrates, each with various plating layers formed in this manner, were subjected to reflow treatment. The reflow conditions are shown in Table 2. The reflow treatment atmosphere was air. Comparative Example 11 was cooled immediately after the first heat treatment without performing the second heat treatment.

[0059] [Table 2]

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

[0061] (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 thicknesses of the tin and nickel layers were measured using a Hitachi High-Tech Science Corporation FT150 X-ray fluorescence film thickness gauge. The nickel layer was left as is. For 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 measured using an X-ray fluorescence film thickness gauge. Then, the tin layer was removed by immersing it for several minutes in an etching solution for removing tin plating films, such as L80 from Leybold Corporation, which consists of components that etch tin but do not corrode the copper-tin alloy. The thickness of the tin-containing layer after etching was then measured again using an X-ray fluorescence film thickness gauge. The average thickness of the tin layer was then calculated by subtracting the thickness of the tin-containing layer after etching from the thickness of the tin-containing layer before etching.

[0062] 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 (convex) 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 distances was then calculated and converted to the actual length to obtain the average thickness of the copper-tin alloy layer.

[0063] (Average thickness of the protrusions in Cu6Sn5 alloy, radius of curvature of the protrusion surface) The thickness of the protrusions and the radius of curvature of the protrusion surface of the Cu6Sn5 alloy were calculated using the image processing software imageJ (ver. 1.54f) on the obtained SIM images. The thickness of the protrusions of the Cu6Sn5 alloy was obtained from 50 Cu6Sn5 alloy protrusions from a cross-sectional SIM image parallel to the rolling direction of the substrate, and the average value was calculated. In this case, the thickness was measured at the widest point in the horizontal direction of the cross-sectional SIM image. The radius of curvature of the convex surface was obtained for 10 convex areas from a cross-sectional SIM image parallel to the rolling direction of the substrate, and the average value was calculated. In this case, the curvature was obtained using "Kappa," a curvature calculation function in the image processing software imageJ, and the average value was calculated by taking the reciprocal of the curvature. In "Kappa," the Curve Input Type was set to B-Spline and the B-Spline Type to Closed. The curvature of the convex surface of each Cu6Sn5 alloy was obtained by fitting the shape of the convex area of ​​the Cu6Sn5 alloy from the cross-section to an ellipse by tracing the contour from convex to convex area of ​​the Cu6Sn5 alloy, and then obtaining the value at the highest point of the convex area of ​​a single Cu6Sn5 alloy.

[0064] (Average KAM value for Cu6Sn5 alloy) For crystal orientation measurement using electron backscatter diffraction to calculate KAM (Kernel Average Misorientation) of Cu6Sn5 alloy, an EBSD (Electron Beam Scanning Microscope) analyzer (JEOL Ltd. 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 analyzer was set to 15kV, and the measurement area was 50μm², the cross-sectional area of ​​Cu6Sn5. 2 The step size for crystal orientation measurement was set to 0.02 μm. The data obtained from the EBSD measurement device was processed using analysis software, and the average KAM value of the Cu6Sn5 alloy was measured by considering the difference in crystal orientation between adjacent measurement points of 5° or more as grain boundaries. Note that the average KAM value of the Cu6Sn5 alloy was not measured for alloys that did not meet the predetermined average thickness of the copper-tin alloy layer.

[0065] (Coefficient of friction) Each sample was cut into a 60mm long test piece parallel to the rolling direction of the base material 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 12 (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 1.5mm was made in the center of the test piece. For measurement, a friction and wear tester (UMT-Tribolab) from Bruker AXS Corporation was used, and the male terminal test piece was set horizontally, with the convex surface of the female terminal test piece in contact with the male terminal test piece at a position 5mm below A in Figure 1, so that A in Figure 1 was the center of the sliding part, and while applying a load of 2 to the male terminal test piece, it was slid for a distance of 10mm to a position 5mm above 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.

[0066] (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.

[0067] (Resistant to micro-sliding wear) Similar to the measurement of friction coefficient and contact resistance, test specimens were prepared and their resistance to micro-sliding abrasion was evaluated. For the measurement, a friction and abrasion tester (UMT-Tribolab) from Bruker AXS Corporation was used. The convex surface of the female test specimen was brought into contact with part A in Figure 1 of the horizontally positioned male terminal test specimen, and the male terminal test specimen was slid back and forth over a sliding distance of 1 mm while a load of 2 N was applied. The sliding speed was set to 1.3 mm / s, and one sliding cycle was considered to be the time it took for the convex surface of the female test specimen to slide 1 mm from part A and then return to part A. The resistance to micro-sliding abrasion was classified by the number of sliding cycles at which the base material was exposed. Those in which the base material was not exposed even after 100 or more sliding cycles were classified as A, those in which the base material was exposed between 25 and 99 sliding cycles were classified as B, and those in which the base material was exposed in less than 25 sliding cycles were classified as C.

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

[0069] [Table 3]

[0070] Examples 1 to 14, in which the average thickness of the nickel layer was 0.30 μm or more and 3.00 μm or less, the average thickness of the copper-tin alloy layer was 0.30 μm or more and 1.20 μm or less, the average thickness of the tin layer was 0.15 μm or more and 0.80 μm or less, the average thickness of the protrusions of the Cu6Sn5 alloy in the copper-tin alloy layer was 0.80 μm or more and 3.00 μm or less, and the average KAM value of the Cu6Sn5 alloy was 0.55° or more and 0.80° or less, showed low coefficient of friction and contact resistance after heating, and good resistance to micro-sliding wear, as evaluated in A and B.

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

[0072] On the other hand, in Comparative Examples 1 and 3, the average value of the KAM of the Cu6Sn5 alloy, the thickness of the protrusions of the Cu6Sn5 alloy, and the radius of curvature of the protrusion surface were not measured because the copper-tin alloy layer was thin. This is thought to be due to insufficient first heat treatment. In contrast, Comparative Example 2 had a thick copper-tin alloy layer, a large average thickness of the protrusions of the Cu6Sn5 alloy, and a low average KAM of the Cu6Sn5 alloy. As a result, it had poor resistance to micro-sliding wear and a high coefficient of friction. Also, because the tin layer was thin, the contact resistance after heating was high. This is thought to be due to excessive heat treatment in the first step. Comparative Example 4 had a small average thickness of the protrusions of the Cu6Sn5 alloy, and Comparative Example 8 also had a small average thickness of the protrusions of the Cu6Sn5 alloy. In both cases, the poor resistance to micro-sliding wear was likely due to insufficient second heat treatment. On the other hand, Comparative Examples 5 and 10 had a large average thickness of the protrusions of the Cu6Sn5 alloy, and both exhibited poor resistance to micro-sliding wear. This is likely due to excessive second heat treatment. Comparative Example 6 had a thick copper-tin alloy layer and a thin tin layer. The average thickness of the protrusions of the Cu6Sn5 alloy was large. As a result, it had poor resistance to micro-sliding wear and the contact resistance after heating was also high. This is thought to be due to excessive first heat treatment. Normally, the average thickness of the protrusions of the Cu6Sn5 alloy is adjusted in the second heat treatment, but in Comparative Example 6, the first heat treatment was excessive, so it is assumed that the adjustment could not be fully made in the second heat treatment. In Comparative Example 7, the contact resistance increased after heating because the nickel layer was thin. Comparative Example 9 had a high coefficient of friction because the tin layer was too thick. Comparative Example 11 had a low average KAM value for the Cu6Sn5 alloy and a small average thickness of the protrusions on the Cu6Sn5 alloy. Therefore, it exhibited poor resistance to micro-sliding wear. This is thought to be due to cooling without performing the second heat treatment. [Explanation of symbols]

[0073] 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-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 0.30 μm or more and 3.00 μm or less, the average thickness of the copper-tin alloy layer is 0.30 μm or more and 1.20 μm or less, and the average thickness of the tin layer is 0.15 μm or more and 0.80 μm or less, and Cu is present in the copper-tin alloy layer at the interface with the tin layer, which has an uneven shape. ６ Sn ５ Having an alloy, the Cu in a cross-section parallel to the rolling direction of the base material ６ Sn ５ The average thickness of the protrusions of the alloy is 0.80 μm or more and 3.00 μm or less, and the Cu in the cross-section parallel to the rolling direction ６ Sn ５ A terminal material for connectors characterized in that the average KAM value of the alloy is 0.55° or more and 0.80° or less.

2. The Cu in a cross-section of the substrate parallel to the rolling direction ６ Sn ５ The connector terminal material according to claim 1, characterized in that the radius of curvature of the convex surface of the alloy is 0.40 μm or more and 2.00 μm 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 comprises a first heat treatment in which the plated substrate is heated in a furnace at a temperature of 240°C to 380°C for a time of 5 seconds to 30 seconds to dissolve the tin plating layer, and a second heat treatment in which the plated substrate is heated in a furnace at a temperature of 150°C to 235°C for a time of 10 seconds to 60 seconds after the first heat treatment, and a coating is formed on the substrate by cooling after the second heat treatment, wherein a nickel layer made of nickel or a nickel alloy with an average thickness of 0.30 μm to 3.00 μm, a copper-tin alloy layer made of a copper-tin alloy with an average thickness of 0.30 μm to 1.20 μm, and a tin layer made of tin or a tin alloy with an average thickness of 0.15 μm to 0.80 μm are laminated in this order on the substrate.

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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