Connector terminal material, method for manufacturing the same, and connector

Abstract

A terminal material for a connector, in which a base material composed of copper or a copper alloy has a coating film formed on a surface thereof, and the coating film has a nickel layer formed on the surface of the base material and composed of nickel or a nickel alloy, a copper-tin alloy layer formed on the nickel layer and composed of an alloy of copper and tin, and a tin layer formed on the copper-tin alloy layer and composed of tin or a tin alloy, the average thickness of the nickel layer is 0.05 μm or more and 3.00 μm or less, and the arithmetic average curvature of peak top points on the surface of the copper-tin alloy layer, Spc, is 700 mm ‑1 and 2200 mm ‑1 Hereinafter, the average thickness of the tin layer is 0.05 μm or more and 2.00 μm or less, and the average thickness of the copper-tin alloy layer is 0.15 μm or more and 1.55 μm or less.

Description

Technical Field

[0001] This invention relates to a connector terminal material with a reduced surface friction coefficient, a method for manufacturing the same, and a connector.

[0002] This application claims priority based on Japanese Patent Application No. 2024-8424 filed on January 24, 2024 and Patent Application No. 2024-154278 filed on September 6, 2024, the contents of which are incorporated herein by reference. Background Technology

[0003] Previously, an automotive connector used in electrical wiring connections in automobiles and other vehicles was known. The automotive connector (automotive terminal) has a terminal pair designed to make electrical connection with a male terminal inserted into the female terminal through contact tabs provided on the female terminal, using a specified contact pressure.

[0004] As such connectors (terminals), there are known terminal materials that are copper-plated and tin-plated on a copper or copper alloy plate and then reflow soldered, thereby forming a copper-tin alloy layer and a tin layer on the copper or copper alloy plate, which have excellent wear resistance.

[0005] As a terminal material having such a copper-tin alloy layer and a tin layer formed, for example in Patent Document 1, the insertion force is reduced by controlling the exposure state of the copper-tin alloy layer from the tin layer by controlling the roughness of the substrate. However, in order to control the roughness of the substrate, it is necessary to perform pre-processing.

[0006] Furthermore, in Patent Document 2, the insertion force is reduced by making the tin layer or tin alloy layer on the copper-tin alloy layer very thin. However, due to the small amount of tin layer, there is a problem of increased contact resistance after heating.

[0007] Furthermore, in Patent Document 3, by replacing a portion of the copper-tin alloy with nickel (Ni), the copper-tin alloy is made into a steep, uneven shape, leaving a tin layer of more than 0.2 μm and less than 0.6 μm, thereby reducing friction and preventing the contact resistance from increasing during heating. However, due to the steepness of the copper-tin alloy layer, there is a problem that it is easily shaved off during sliding and has poor wear resistance.

[0008] Patent Document 1: Japanese Patent Application Publication No. 2007-100220

[0009] Patent Document 2: Japanese Patent Application Publication No. 2011-012320

[0010] Patent Document 3: Japanese Patent Application Publication No. 2014-240520

[0011] In the terminal materials described in these patent documents, the proportion of a hard copper-tin alloy layer is increased by thinning the surface tin layer to reduce the coefficient of friction. The soft tin layer is prone to sticking during insertion, which leads to a problem of increased insertion force. Therefore, to prevent this sticking, it is preferable to expose the copper-tin alloy layer on the outermost surface. However, this results in high contact resistance at high temperatures and insufficient resistance to micro-sliding wear. Summary of the Invention

[0012] The present invention was made in view of this situation, and its purpose is to control the surface shape of the copper-tin alloy layer, reduce the coefficient of friction, and improve wear resistance and heat resistance.

[0013] The connector terminal material of the present invention has a coating formed on the surface of a substrate made of copper or a copper alloy, and the coating comprises: a nickel layer formed on the surface of the substrate and made of nickel or a nickel alloy; a copper-tin alloy layer formed on the nickel layer and made of an alloy of copper and tin; and a tin layer formed on the copper-tin alloy layer and made of tin or a tin alloy, wherein the average thickness of the nickel layer is 0.05 μm or more and 3.00 μm or less, and the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer is 700 mm. -1 Above and 2200mm -1 Hereinafter, the average thickness of the tin layer is 0.05 μm or more and 2.00 μm or less, and the average thickness of the copper-tin alloy layer is 0.15 μm or more and 1.55 μm or less.

[0014] A smaller arithmetic mean curvature Spc at the peak indicates a more rounded tip, while a larger arithmetic mean curvature Spc indicates a sharper tip. If the arithmetic mean curvature Spc at the peak is less than 700 mm... -1 The surface shape of the copper-tin alloy layer (the interface shape with the tin layer) becomes smoother, increasing the contact area with the other terminal and thus raising the coefficient of friction. Furthermore, wear resistance decreases. On the other hand, if the arithmetic mean curvature Spc of the peak exceeds 2200 mm... -1 The surface of the copper-tin alloy layer becomes sharper, making it easier to chip away during sliding, thus increasing the coefficient of friction. Furthermore, its wear resistance decreases.

[0015] In this case, if the average thickness of the tin layer is less than 0.05 μm, the contact resistance will be high in high-temperature environments. If it exceeds 2.00 μm, adhesive wear will easily occur during sliding, and the coefficient of friction will be high.

[0016] Furthermore, when the average thickness of the copper-tin alloy layer is less than 0.15 μm, the arithmetic mean curvature Spc at the peak decreases, thus increasing the coefficient of friction and reducing wear resistance. If the average thickness of the copper-tin alloy layer exceeds 1.55 μm, the arithmetic mean curvature Spc at the peak increases, thus increasing the coefficient of friction and reducing wear resistance.

[0017] The nickel layer effectively prevents copper from diffusing from the substrate at high temperatures. However, if its average thickness is less than 0.05 μm, the effect of preventing copper diffusion is poor, leading to a faster formation of a copper-tin alloy and higher contact resistance. If the average thickness of the nickel layer exceeds 3.00 μm, cracks may occur during bending processes.

[0018] In the connector terminal material of the present invention, the roundness of the copper-tin alloy particles on the surface of the copper-tin alloy layer is preferably 0.5 or more.

[0019] The closer the roundness is to 1, the closer it is to a perfect circle, resulting in stable contact and a good coefficient of friction. If the roundness is less than 0.5, the function of the contact becomes uneven, the coefficient of friction increases slightly, and the wear resistance decreases slightly.

[0020] In the connector terminal material of the present invention, the tin layer of the coating is removed to expose the copper-tin alloy layer, and a portion of the copper-tin alloy layer is exposed on the surface of the exposed tin layer. The exposed area ratio of the copper-tin alloy layer on the surface of the tin layer is preferably 5% or more and 70% or less.

[0021] By exposing a copper-tin alloy layer, which is harder than tin, on the surface, the friction coefficient can be reduced in combination with the lubricating effect of the soft tin layer. When the exposed area of ​​this copper-tin alloy layer is less than 5%, the effect of reducing the friction coefficient is poor. If the exposed area exceeds 70%, the area occupied by the tin layer on the surface becomes smaller, and the contact resistance may increase in high-temperature environments.

[0022] In the connector terminal material of the present invention, it is preferable to have a connecting portion that connects to the other side and a substrate fixing portion that is fixed to the substrate, and the coating is formed at least in the connecting portion.

[0023] In this case, a tin surface layer with a surface made of tin or a tin alloy can be formed on the entire surface of the front and back sides and both sides of the substrate fixing part.

[0024] By forming the aforementioned film at least at the connection portion, it becomes a terminal with excellent insertability.

[0025] Furthermore, in connector terminal materials that need to be fixed to a substrate, it is preferable to use a "post-plating method" in which plating is performed after punching the metal plate. It is preferable that the aforementioned coating is formed at least on the connection portion connected to the other side, and a tin surface layer with a surface composed of tin or tin alloy is formed at least on the entire surface of the fixing portion to the substrate.

[0026] In the pin-shaped terminal, a tin surface layer composed of tin or tin alloy is formed on the entire surface of the substrate fixing part, thereby providing excellent solderability, and the aforementioned coating is formed at the connection part with the other side, thereby making it a terminal with excellent insertion performance.

[0027] The connector of the present invention has a side terminal and a side terminal that can be interconnected, at least one of which can be made of the connector terminal material, and the difference in the arithmetic mean curvature Spc of the peaks on the surfaces of the copper-tin alloy layers of the side terminal and the side terminal is within 200 mm. -1 Above and 1200mm -1 Within the following range.

[0028] By setting the difference in the arithmetic mean curvature Spc at the peak vertices to 200 mm -1 Above and 1200mm -1 Within the following range, the actual contact area becomes smaller, thus reducing the sliding marks and further lowering the coefficient of friction.

[0029] Furthermore, when the difference in roundness of the copper-tin alloy particles on the surface of the copper-tin alloy layer of the terminal on one side and the terminal on the other side is within the range of 0.4 or less, the coefficient of friction can be further reduced.

[0030] The method for manufacturing connector terminals of the present invention includes: a plating layer forming step, wherein 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 are sequentially stacked on the surface of a substrate made of copper or a copper alloy to form a substrate with plating layers; and a reflow soldering process, wherein the substrate with plating layers is subjected to a reflow soldering process of heating. In the plating layer forming step, the thickness of the nickel plating layer is formed to be 0.05 μm or more and 3.00 μm or less, the thickness of the copper plating layer is formed to be 0.10 μm or more and 0.70 μm or less, and the thickness of the tin plating layer is formed to be 0.20 μm or more and 2.90 μm or less. The soldering process includes: a first heating treatment, in which the substrate with the plating layer is passed through a first heating furnace at a first furnace temperature of 150°C or higher and 270°C or lower for a period of 3 seconds or more and 30 seconds under atmospheric conditions, heating the substrate with the plating layer to a temperature lower than the melting point of tin; a second heating treatment, in which, after the first heating treatment, the substrate with the plating layer is passed through a second heating furnace at a second furnace temperature of 232°C or higher and 350°C or lower than the first furnace temperature for a period of 3 seconds or more and 35 seconds; and a cooling treatment, in which the substrate with the plating layer is rapidly cooled immediately after the tin plating layer has melted through the second heating treatment.

[0031] By setting the reflow soldering process to a two-stage heating at a specified temperature followed by cooling, the arithmetic mean curvature Spc of the peaks on the surface of the aforementioned copper-tin alloy layer can be controlled within a specified range. In this case, the copper-tin alloy is grown in the first heating treatment and melted in the second heating treatment to form a copper-tin alloy layer of a specified shape. Therefore, the temperature of the second heating treatment needs to be higher than that of the first heating treatment. If the first and second heating treatments are set to the same temperature, or if the temperature of the second heating treatment is lower than that of the first heating treatment, it is impossible to form the copper-tin alloy layer of the specified shape, and it is difficult to control the arithmetic mean curvature Spc of the peaks on its surface within the specified range. In addition, the plating layer changes during the reflow soldering process, but before the end of the reflow soldering process, it is called a substrate with a plating layer.

[0032] If the reflow soldering process is not heated sufficiently, the average thickness of the copper-tin alloy layer will be less than 0.15 μm; if the reflow soldering process is heated excessively, the average thickness of the copper-tin alloy layer will exceed 1.55 μm.

[0033] In the first heating process of this reflow soldering process, the substrate with the plating layer is heated to a temperature below the melting point of tin, so as not to melt the tin plating layer. In the second heating process, after the outermost tin plating layer melts and becomes glossy, the cooling process is immediately initiated. Therefore, in the second heating process, the substrate with the plating layer is always in a state of rising temperature and will not remain at the peak temperature of tin melting.

[0034] Here, the shape of the copper-tin alloy layer is affected not only by the reflow soldering conditions but also by the thickness of the tin plating layer and the copper plating layer. The effects of the thickness of the tin plating layer and the copper plating layer are explained below. When the copper plating layer thickness is 0.10 μm or more and the tin plating layer thickness is less than 0.20 μm, residual copper plating is observed, resulting in a smaller Spc (spec) and a higher coefficient of friction, leading to decreased wear resistance. Furthermore, due to the thin tin layer, the contact resistance is higher. If the copper plating layer thickness is less than 0.10 μm, a portion of the copper-tin alloy is replaced by nickel, resulting in a steeper shape of the copper-tin alloy layer, a larger Spc, a higher coefficient of friction, and decreased wear resistance.

[0035] In addition, during the cooling process, it is preferable to set the cooling time for the substrate with the coating layer until the temperature reaches 50°C to be 4 seconds or more and 60 seconds or less.

[0036] According to the present invention, by controlling the surface of the copper-tin alloy layer to a specified shape, the coefficient of friction can be reduced and the wear resistance and heat resistance can be improved. Attached Figure Description

[0037] Figure 1 This is a plan view of the connector terminal material according to an embodiment of the present invention.

[0038] Figure 2 yes Figure 1 A schematic cross-sectional view of the connector terminal material.

[0039] Figure 3 It means Figure 1 A flowchart of a method for manufacturing connector terminal materials.

[0040] Figure 4 It means Figure 2 A schematic cross-sectional view of a substrate with a plating layer before the reflow soldering process of connector terminal materials.

[0041] Figure 5 This is a backscattered electron (BSE) image of the cross section of sample 3. Detailed Implementation

[0042] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0043] [Structure of connector terminals]

[0044] like Figure 1 As shown, the connector terminal 1 in this embodiment is a terminal chain formed by connecting multiple pin-shaped terminal portions 10, and is formed by stamping a long strip of sheet metal.

[0045] Specifically, a plurality of terminal portions 10 are arranged side by side between a pair of elongated connecting members 11 and 12, along the direction connecting the two connecting members 11 and 12. Each terminal portion 10 has a needle-shaped connecting portion 13, a wide shoulder portion 14, and a substrate fixing portion 15 continuously formed from its front end, and its two ends (the front end of the connecting portion 13 and the base end of the substrate fixing portion 15) are respectively connected to the connecting members 11 and 12. The terminal portion 10 is used to be fixed to the substrate or the like in an electrically connected state by pressing the substrate fixing portion 15 into or welding it to a through hole in the substrate, and is electrically connected by inserting the connecting portion 13 into other female terminals.

[0046] Furthermore, the shape of the terminal is just one example and is not limited to this. Figure 1 The shape shown is acceptable as long as it has a connection part that allows for electrical connection with the other terminal.

[0047] And, as Figure 2 As schematically shown in the cross section, the connector terminal material 1 has a coating 22 formed on a substrate 21 made of copper or a copper alloy. As the coating 22, a nickel layer 23 made of nickel or a nickel alloy, a copper-tin alloy layer 24 made of an alloy of copper and tin, and a tin layer 25 made of tin or a tin alloy are formed in sequence.

[0048] exist Figure 2 The cross-section in the thickness direction is shown, but the film 22 is formed on the entire surface of the front and back sides and the two sides of the substrate 21.

[0049] The composition of the substrate 21 is not particularly limited as long as it is made of copper or copper alloy. For example, it can be made of a plate made of oxygen-free copper (C10200) or Cu-Mg copper alloy (C18665), brass, phosphor bronze, or other copper or copper alloy.

[0050] The nickel layer 23 has the function of suppressing the diffusion of copper from the substrate 21 to the copper-tin alloy layer 24 and tin layer 25 formed on the nickel layer 23. The average thickness (film thickness) of the nickel layer 23 is 0.05 μm or more and 3.00 μm or less. If the average thickness of the nickel layer 23 is less than 0.05 μm, the effect of preventing copper diffusion from the substrate 21 is poor at high temperatures, the rate of copper-tin alloy formation increases, and the contact resistance increases. On the other hand, if the average thickness of the nickel layer 23 exceeds 3.00 μm, cracks may occur during bending processing. In addition, the composition of the nickel layer 23 is not particularly limited as long as it is made of nickel or a nickel alloy. The average thickness of the nickel layer 23 is preferably 0.10 μm or more and 2.00 μm or less.

[0051] 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 soldering process. The interface between the surface of the copper-tin alloy layer 24 and the tin layer 25 thereon is formed in an uneven shape, with a portion of it exposed on the surface of the tin layer 25. The average thickness of the copper-tin alloy layer 24 is 0.15 μm or more and 1.55 μm or less. The average thickness of the copper-tin alloy layer 24 and the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24 are affected by the reflow soldering conditions described later and the thickness of the tin plating layer 33 and the copper plating layer 32 during manufacturing.

[0052] Regarding the impact of reflow soldering conditions, firstly, if the average thickness of the copper-tin alloy layer 24 is less than 0.15 μm due to insufficient heating during reflow soldering, the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24 (described later) decreases, the exposed area ratio on the surface of the tin layer 25 decreases, and the coefficient of friction increases. Furthermore, since the hard copper-tin alloy layer 24 has a thin average thickness, its wear resistance decreases. On the other hand, if the average thickness of the copper-tin alloy layer 24 exceeds 1.55 μm due to excessive heating during reflow soldering, the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24 increases, the coefficient of friction increases, and wear resistance decreases. The lower limit of the average thickness of the copper-tin alloy layer 24 is preferably 0.31 μm.

[0053] Regarding the effects of the thickness of the tin plating layer 33 and the copper plating layer 32 during manufacturing, firstly, when the thickness of the copper plating layer is 0.10 μm or more and the thickness of the tin plating layer is less than 0.20 μm, residual copper plating layer is observed, resulting in a smaller Spc (spec) and a higher coefficient of friction, thus reducing wear resistance. Furthermore, due to the thin tin layer, the contact resistance is higher. On the other hand, if the thickness of the copper plating layer is less than 0.10 μm, a portion of the copper-tin alloy is replaced by nickel, resulting in a steeper shape of the copper-tin alloy layer, a larger Spc, a higher coefficient of friction, and reduced wear resistance.

[0054] Furthermore, the exposed area ratio of the copper-tin alloy layer 24 on the surface of the tin layer 25 is preferably 5% or more and 70% or less. By exposing the copper-tin alloy layer 24, which is harder than the tin layer 25, on the surface, the friction coefficient can be reduced in combination with the lubricating effect of the soft tin layer 25. When the exposed area ratio of the copper-tin alloy layer 24 is less than 5%, the effect of reducing the friction coefficient is poor, and the surface area of ​​the tin layer 25 increases accordingly, thus making adhesive wear more likely, and the friction coefficient may increase. Furthermore, the wear resistance may also decrease. If the exposed area ratio exceeds 70%, the area occupied by the tin layer 25 on the surface becomes smaller, and the contact resistance may increase under high temperature environments. The exposed area ratio of the copper-tin alloy layer 24 is more preferably set to 10% or more and 50% or less.

[0055] Furthermore, the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24, measured after removing the tin layer 25, is 700 mm. -1 Above and 2200mm -1 The arithmetic mean curvature Spc of the peak is a parameter measured according to ISO 25178. A smaller value indicates a more rounded tip, while a larger value indicates a sharper tip. If the arithmetic mean curvature Spc of the peak is less than 700 mm... -1 The surface shape of the copper-tin alloy layer 24 (the interface shape with the tin layer 25) becomes smoother. Furthermore, the exposed area ratio decreases, and correspondingly, the area occupied by the tin layer 25 on the surface of the film 22 tends to increase. Therefore, the coefficient of friction increases, and the wear resistance decreases.

[0056] On the other hand, if the arithmetic mean curvature Spc at the peak exceeds 2200 mm -1 This results in a sharper surface shape for the copper-tin alloy layer 24, making it easier for the layer to be chipped away during sliding, thus increasing the coefficient of friction. Furthermore, wear resistance decreases. The arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24 is preferably 900 mm. -1 Above and 1900mm -1 the following.

[0057] Furthermore, the roundness of the copper-tin alloy particles on the surface of the copper-tin alloy layer 24 (at the interface with the tin layer 25) is preferably 0.5 or higher. This roundness is calculated by 4π × (particle area) ÷ (circumference). 2 Definition. The closer the roundness of the copper-tin alloy particles is to 1, the closer they are to a perfect circle. When viewed from the surface, they are set to a near-circular state, thus providing stable contact and achieving a low coefficient of friction.

[0058] If the roundness of the copper-tin alloy particles is less than 0.5, the contact points between the copper-tin alloy layer 24 exposed on the surface of the tin layer 25 and the sliding counterpart terminal become uneven during connector sliding, potentially increasing the coefficient of friction. Furthermore, wear resistance may slightly decrease. A roundness of 0.55 or higher is more preferable for the copper-tin alloy particles. Additionally, a higher roundness of the copper-tin alloy particles results in a lower coefficient of friction, which is desirable, but in practice, it is difficult to control the shape of the copper-tin alloy layer 24 to a roundness exceeding 0.85.

[0059] The tin layer 25 is a layer composed of tin or a tin alloy, with an average thickness of 0.05 μm or more and 2.00 μm or less. If the average thickness of the tin layer is less than 0.05 μm, the contact resistance becomes high at high temperatures; if it exceeds 2.00 μm, adhesive wear is more likely to occur, and the coefficient of friction becomes higher. Furthermore, the exposed area of ​​the copper-tin alloy layer 24 also decreases. The average thickness of the tin layer 25 is preferably 0.05 μm or more and 1.00 μm or less, and more preferably 0.10 μm or more and 0.50 μm or less.

[0060] [Manufacturing method for connector terminals]

[0061] Next, the manufacturing method of the connector terminal 1 will be described.

[0062] like Figure 3 As shown, the manufacturing method of the connector terminal 1 includes: a punching process, in which a slender plate is punched to form a terminal chain body that becomes a substrate 21; a pretreatment process, in which the surface of the punched substrate 21 is cleaned; a plating layer forming process, 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 substrate 21; and a reflow soldering process, in which the substrate 35 with the three plating layers 31 to 33 is heated and reflow soldered. The process sequence will be described below.

[0063] (Punching process)

[0064] While releasing the slender sheet metal wound into a coil shape, it is simultaneously punched and cut to form a shape like... Figure 1 The terminal chain of the substrate 21 shown.

[0065] [Pretreatment process]

[0066] The surface of the die-cut substrate 21 is cleaned by degreasing, pickling, etc.

[0067] (Platinum coating formation process)

[0068] -Nickel plating-

[0069] The surface of the pretreated substrate 21 is subjected to a nickel plating process to form a nickel plating layer 31 composed of nickel or a nickel alloy. A general nickel plating bath can be used, for example, an aminosulfonic acid bath with nickel sulfamate, nickel chloride, and boric acid as the main components. The temperature of the plating bath is 40°C or higher and 60°C or lower, and the current density is 1 A / dm³. 2 Above and 10A / dm 2 The thickness of the nickel plating layer 31 is 0.05 μm or more and 3.00 μm or less.

[0070] -Copper plating-

[0071] A copper plating process is performed to form a copper plating layer 32 composed of copper or a copper alloy on a nickel plating layer 31. A general copper plating bath can be used for copper plating; for example, a copper sulfate bath with copper sulfate and sulfuric acid as the main components can be used. The temperature of the plating bath is above 20°C and below 60°C, and the current density is 1 A / dm³. 2 Above and 10A / dm 2 the following.

[0072] The thickness of the copper plating layer 32 is 0.10 μm or more and 0.70 μm or less. When the thickness of the copper plating layer is 0.10 μm or more and the thickness of the tin plating layer is less than 0.20 μm, copper plating residue is observed after the reflow soldering process, resulting in a smaller Spc (spc), a higher coefficient of friction, and reduced wear resistance. If the thickness of the copper plating layer 32 exceeds 0.70 μm, the exposed area ratio of the copper-tin alloy layer 24 exposed from the surface of the tin layer 25 after the reflow soldering process increases, potentially leading to higher contact resistance. On the other hand, if the thickness of the copper plating layer 32 is less than 0.10 μm, a portion of the copper-tin alloy is replaced by nickel, resulting in a steeper shape of the copper-tin alloy layer, a larger Spc, a higher coefficient of friction, and potentially reduced wear resistance. The exposed area ratio of the copper-tin alloy layer 24 may also decrease. The thickness of the copper plating layer 32 is preferably 0.20 μm or more and 0.50 μm or less. The lower limit of the thickness of the copper plating layer 32 is more preferably 0.30 μm.

[0073] -Tin plating-

[0074] A tin plating process is performed to form a tin plating layer 33 composed of tin or a tin alloy on a 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 with methanesulfonic acid and tin methanesulfonate as the main components can be used. The temperature of the plating bath is 20°C or higher and 40°C or lower, and the current density is 1 A / dm³. 2 Above and 20A / dm 2 the following.

[0075] The thickness of the tin plating layer 33 is set to be 0.20 μm or more and 2.90 μm or less. If the thickness of the tin plating layer 33 is less than 0.20 μm, the average thickness of the tin layer 25 after the reflow soldering process becomes thinner, and therefore the contact resistance may increase under high temperature conditions. If the thickness of the tin plating layer 33 exceeds 2.90 μm, the tin layer 25 after the reflow soldering process becomes thicker, the exposed area of ​​the copper-tin alloy layer 24 decreases, adhesive wear is more likely to occur, and therefore the coefficient of friction may increase. The thickness of the tin plating layer 33 is more preferably 0.20 μm or more and 1.30 μm or less, and even more preferably 0.40 μm or more and 1.00 μm or less.

[0076] Thus, by sequentially forming a nickel plating layer 31, a copper plating layer 32, and a tin plating layer 33 on the surface of the substrate 21, as... Figure 4 As shown, a substrate 35 with three plating layers 31 to 33 is obtained. In this case, the substrate 21 before plating is in a state of being punched and cut into a chain-terminal shape. The substrate 21 is immersed in a plating bath to form plating layers 31 to 33. Therefore, three plating layers 31 to 33 are formed not only on the front and back sides 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 where a portion of the substrate is immersed in a plating bath.

[0077] (Reflow soldering process)

[0078] As described above, the substrate 35 with the plating layers 31 to 33 is subjected to reflow soldering. In this reflow soldering process, when a long, thin sheet (strip) is wound onto a roller, the sheet is continuously subjected to the aforementioned pretreatment and plating processes while being moved along its length, and the sheet is then processed in a reflow oven. However, in the case of the substrate 35 with the plating layers in this embodiment, it is pre-processed by stamping, etc. Figure 1 The punched material, which is punched to a specified length as shown, is subjected to the above-mentioned pretreatment and plating treatment on the punched material, and the substrate 35 with the plating layer is supplied to a relatively small reflow oven for reflow soldering treatment.

[0079] Specifically, the process includes: a first heating treatment in which the substrate 35 with the plating layer is passed through a first heating furnace at a first furnace temperature of 150°C or higher and 270°C or lower in an atmospheric atmosphere for a period of 3 seconds or more and 30 seconds to heat it to a temperature lower than the melting point of tin; a second heating treatment in which the substrate 35 with the plating layer is passed through a second heating furnace at a second furnace temperature of 232°C or higher and 350°C or lower than the first furnace temperature for a period of 3 seconds or more and 35 seconds to heat it; and a cooling treatment in which the substrate 35 with the plating layer is rapidly cooled immediately after the tin plating layer has melted through the second heating treatment.

[0080] In this reflow soldering process, a two-stage heating process—heating to near the melting temperature of the tin plating layer 33 followed by further reflow soldering to melt it—allows the copper-tin alloy particles and tin particles formed by the copper plating layer 32 and the tin plating layer 33 to grow slowly and be controlled to have a rounded shape. This allows the arithmetic mean curvature Spc and roundness of the peaks on the surface of the aforementioned copper-tin alloy layer 24 to be controlled within a specified range.

[0081] In addition, the atmosphere for the first and second heating treatments in this reflow soldering process can be in the atmosphere, or water vapor can be added.

[0082] In this case, during the first heat treatment, the furnace temperature is sometimes at a high temperature, for example, 270°C, but the substrate 35 with the plating layer does not rise to the melting temperature of tin, so the tin plating layer 33 does not melt at this stage. This first heat treatment is a pre-stage used in the second heat treatment to rapidly melt the tin plating layer 33.

[0083] In this first heat treatment, if the temperature inside the first furnace is less than 150°C or the time is less than 3 seconds, the heating is insufficient, and the formation of the copper-tin alloy in the second heat treatment is insufficient. It is difficult to form a copper-tin alloy layer 24 with the desired average thickness. In addition, the arithmetic mean curvature Spc of the peaks on the surface of the aforementioned copper-tin alloy layer is small, and the roundness is small, making it difficult to reliably control within the specified range. On the other hand, if the temperature inside the first furnace exceeds 270°C, or the temperature of the substrate 35 with the plating layer exceeds the melting point of tin and the tin plating layer 33 melts in the first heat treatment, the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24 becomes larger, thus reducing wear resistance. Furthermore, the tin layer 25 becomes thinner, and the contact resistance becomes higher. When the time exceeds 30 seconds, it becomes overheating, the tin layer 25 becomes thinner, and the contact resistance becomes higher.

[0084] Furthermore, in the second heat treatment, if the temperature inside the second furnace is less than 232°C or the time is less than 3 seconds, the copper-tin alloy formation is insufficient, making it difficult to form the desired average thickness of the copper-tin alloy layer 24. This results in a smaller Spc (spc), a higher coefficient of friction, and reduced wear resistance. On the other hand, if the temperature inside the second furnace exceeds 350°C, overheating causes an increase in the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24, further increasing the coefficient of friction and reducing wear resistance. Additionally, the tin layer 25 becomes thinner, leading to higher contact resistance. Even when both the temperatures inside the first and second furnaces exceed the specified temperatures, overheating again causes an increase in the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24, resulting in a higher coefficient of friction and reduced wear resistance. Furthermore, the tin layer 25 becomes thinner, leading to higher contact resistance. If the second heat treatment time exceeds 35 seconds, the tin layer 25 becomes thinner, and the contact resistance increases. However, if the tin plating layer 33 is thicker or the copper plating layer 32 is thinner, the tin layer 25 will become thicker even if the heating temperature is higher or the heating time is longer.

[0085] In this second heat treatment, the tin plating layer of the substrate 35 with the plating layer melts. Regarding the melting of the tin plating layer, if the tin of the substrate 35 with the plating layer melts, the surface changes from white to a glossy silver, which can be confirmed.

[0086] In this second heat treatment, after the outermost tin plating layer melts and becomes glossy, it immediately enters the cooling process. Therefore, in this second heat treatment, the substrate 35 with the plating layer is always in a heated state and will not remain at the peak temperature of tin melting.

[0087] Furthermore, regarding the relationship between furnace temperature and furnace time in the reflow soldering process, the higher the furnace temperature, the shorter the time. For example, in the first heating process, if the furnace temperature is close to 150°C, the time is extended to about 30 seconds; if the furnace temperature is close to 270°C, the time is shortened to about 3 seconds. The second heating process is similar: if the furnace temperature is close to 232°C, the time is extended to about 35 seconds; if it is close to 350°C, the time is shortened to about 3 seconds.

[0088] In this case, the relationship between furnace temperature and time can be subdivided within a specified temperature range. For example, in the first heating process, when the furnace temperature is above 150°C and below 200°C, the time is set to be more than 19 seconds and less than 30 seconds; when it is above 200°C and below 250°C, it is set to be more than 8 seconds and less than 19 seconds; and when it is above 250°C and below 270°C, it is set to be more than 3 seconds and less than 8 seconds. In the second heating process, when the furnace temperature is above 232°C and below 280°C, the time is set to be more than 23 seconds and less than 35 seconds; when it is above 280°C and below 320°C, it is set to be more than 11 seconds and less than 23 seconds; and when it is above 320°C and below 350°C, it is set to be more than 3 seconds and less than 11 seconds. This subdivision method can be set simply by considering ease of management.

[0089] In addition, the first heating furnace and the second heating furnace are arranged without gaps, and the substrate 35 with the coating layer passes continuously from the first heating furnace through the second heating furnace.

[0090] Furthermore, during the cooling process, it is preferable to set the cooling time for the substrate 35 with the plating layer to reach 50°C to be 4 seconds or more and 60 seconds or less. Under atmospheric cooling conditions, it is physically difficult to cool the substrate 35 with the plating layer to 50°C in a cooling time of less than 4 seconds. Additionally, if the cooling time exceeds 60 seconds to cool the substrate 35 with the plating layer to 50°C, the formation of the copper-tin alloy will not be sufficiently suppressed, and the alloy shape may not be circular, or the roundness may be reduced.

[0091] The cooling process begins immediately after the tin plating layer of the plated substrate 35 melts during the second heating process, for example, within 2 seconds, preferably within 1 second, after melting. Strictly speaking, the plated substrate 35 is cooled starting near the outlet of the second furnace. Preferably, cooling is achieved by blowing cold air or water onto the plated substrate 35 exiting the second furnace, or by passing the plated substrate 35 through a water bath or the like.

[0092] Through this reflow soldering process, a nickel layer 23, a copper-tin alloy layer 24, and a tin layer 25 are sequentially formed on the substrate 21 as a coating 22. As described above, plating layers 31 to 33 are formed not only on the front and back sides of the substrate 21, but also on both sides. Therefore, the two sides are also formed with a coating 22 consisting of a nickel layer 23, a copper-tin alloy layer 24, and a tin layer 25, just like the front and back sides, so that the entire surface of the substrate 21 is covered by the coating 22.

[0093] In addition, through reflow soldering, the copper in the copper plating layer 32 reacts with the tin in the tin plating layer 33 to form a copper-tin alloy layer 24 and a tin layer 25. However, some of the copper in the copper plating layer 32 may not react and remain, resulting in a thin copper layer between the nickel layer 23 and the copper-tin alloy layer 24.

[0094] When using the pin-shaped terminal of the connector terminal material 1 of this embodiment, such as Figure 1 As shown, the connecting portion 13 that connects to the other terminal is formed into a slender needle shape, so that not only the front and back sides of the connector terminal 1 contact the other terminal, but sometimes the side also contacts the other terminal. Furthermore, since a coating 22 is formed on the entire surface, corrosion is not easily generated.

[0095] Furthermore, the inventors' in-depth research has shown that, in the combination of terminals, by optimizing the shape of the copper-tin alloy layers on both sides, the present invention can achieve further low friction during terminal sliding.

[0096] That is, in a set of terminals that are in a mating state, if the difference in the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24 is set to 200mm -1 Above and 1200mm -1 The following range allows for terminals with lower friction. In this case, it is even more preferable to set the difference in roundness of the copper-tin alloy particles on the surface of the copper-tin alloy layer 24 to be less than 0.4.

[0097] The difference in SPc between the female terminal and the male terminal is 200mm. -1 Above and 1200mm -1 In the following cases, the unevenness of the copper-tin alloy layer 24 is moderately different, so the contact points of the copper-tin alloy layer 24 become multiple points during sliding. The pressure at each contact point becomes smaller, the force is dispersed, and thus the coefficient of friction becomes lower and the amount of wear is reduced.

[0098] Furthermore, in the case of such a combination of terminals, the aforementioned coating 22 only needs to be formed on at least one terminal. Regarding the other terminal, for example, the arithmetic mean curvature Spc and roundness of the peaks on the surface of the copper-tin alloy layer 24 can deviate from the numerical range described in the embodiment (Spc is 700 mm). -1 Above and 2200mm -1 (The following must have a roundness of 0.5 or higher).

[0099] Furthermore, the detailed structure is not limited to the structure of the embodiments, and various modifications can be made without departing from the spirit of the invention.

[0100] In the connector terminal 1 of the embodiment, although the coating 22 is formed on the entire surface of the substrate 21, it is sufficient to form it at least on the connecting portion 13. In this connecting portion 13, even if the coating 22 is not formed on the entire surface of the front and back sides and the two side sides, it is sufficient to form the coating 22 only at the portion that contacts the opposite side component. Furthermore, it is not necessary to form the coating 22 on the entire surface (front and back sides and the two side sides) of the substrate fixing portion 15; it is also possible to have a structure in which the entire surface (front and back sides and the two side sides) has a tin surface layer with a surface made of tin or a tin alloy. The tin surface layer formed when the coating 22 is formed on the substrate fixing portion 15 is called the tin layer 25.

[0101] Example

[0102] As the substrate, CDA (Copper Development Association) alloy designation C18665 with a thickness of 0.40 mm was used. After being punched into the shape of the terminal chain shown in the figure, electrolytic degreasing and pickling were performed as pretreatments. Nickel plating, copper plating, and tin plating were then performed sequentially on the surface. Pickling was performed between the nickel plating and copper plating. The conditions for these electrolytic degreasing, pickling, and plating processes are shown in Table 1 if presented in the order of the processes. The same conditions were used for the following examples and comparative examples. In the table, RT represents room temperature.

[0103] [Table 1]

[0104]

[0105] Thus, reflow soldering was performed on substrates with plating layers of various thicknesses. The thickness of each plating layer and the reflow soldering conditions are shown in Table 2. The cooling time was the time until the temperature of the plating substrate reached 50°C.

[0106] When measuring the thickness of each plating layer before and after reflow soldering, the measuring unit is set to... Figure 1 Part A. Part A is the central part of the terminal connection part 13.

[0107] Regarding the thickness of the copper layer and copper-tin alloy layer in part A where the three-layer plating is formed, the sample was cut off, and resin was filled in such a way that the cut surface became the observation area. After that, it was ground and CP (section polishing) was performed. The cross-sectional reflected electron image was observed using a scanning electron microscope Regulus 8230 manufactured by Hitachi High-Tech Corporation. The thickness at any 10 points was measured and the average value was obtained.

[0108] Furthermore, the thicknesses of the tin and nickel layers in Part A were measured using a fluorescence X-ray film thickness gauge (FT150) manufactured by Hitachi High-Tech Science Corporation.

[0109] [Table 2]

[0110]

[0111] For the terminal materials after reflow soldering, the average thickness of each layer of the coating, the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer, the roundness of the copper-tin alloy particles on the surface of the copper-tin alloy layer, and the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer were measured. The wear resistance (wear amount), friction coefficient, and contact resistance were also evaluated.

[0112] (Average thickness of each layer)

[0113] When measuring the average thickness of each layer, the measuring unit is set to... Figure 1 Part A. Part A is the central part of the terminal connection.

[0114] The thicknesses of the tin and nickel layers were measured using a fluorescence X-ray film thickness gauge (FT150) manufactured by Hitachi High-Tech Science Corporation.

[0115] Regarding the average thickness of the tin layer before and after reflow soldering, the thickness of the tin-containing layer (the tin-containing layer: the tin layer and the copper-tin alloy layer as a whole) of the sample after reflow soldering is first measured. Then, the tin layer is removed by immersing it in an etchant solution for removing a tin-plated film made of tin-etching and non-corroding copper-tin alloy components, such as L80 manufactured by LEYBOLD CO.,LTD., for a few minutes. The average thickness of the tin layer is defined as the difference between the thickness of the tin-containing layer before etching and the thickness of the tin-containing layer after etching.

[0116] Regarding the average thickness of the copper-tin alloy layer, the sample was cut, and the cut surface was used as the observation area. After resin embedding, it underwent grinding and CP (Cross Section Polishing). The cross-sectional reflected electron image was observed using a Regulus 8230 scanning electron microscope manufactured by Hitachi High-Tech Corporation. A schematic diagram of the cross-section is shown below. Figure 2 The thickness of the nickel layer and the copper-tin alloy layer is measured at 10 arbitrary points, including the distance 'a' between the peaks of the nickel layer and the copper-tin alloy layer and the distance 'b' between the valleys of the nickel layer and the copper-tin alloy layer. The height of the copper-tin alloy layer is calculated from (a+b) / 2, and the average value is obtained.

[0117] (The arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer)

[0118] about Figure 1 The arithmetic mean curvature, Spc, of the peak of the connecting portion in section A was measured after the tin layer was removed by immersion in an etching solution for stripping tin-plated films, exposing the underlying copper-tin alloy layer. Spc was then measured over a 20 μm square area using a laser microscope (VK-X200) manufactured by KEYENCE CORPORATION, at 150x objective (measurement field of view 96 μm × 72 μm). The obtained data were filtered with the S-filter cutoff wavelength set to 1 μm and the L-filter cutoff wavelength set to 0.1 mm. The Spc value was calculated based on the average of five measured points.

[0119] (The roundness of the copper-tin alloy particles on the surface of the copper-tin alloy layer)

[0120] After removing the tin layer by immersion in an etching solution for tin plating film stripping, exposing the underlying copper-tin alloy layer, the measurement section was set as section A, and a 0.0008 mm sample was observed at 4000x magnification using a SEM (Scanning Electron Microscope) (JEM JCM-7000 manufactured by JEOLL Ltd.). 2 The secondary electron image of the field of view. The value representing the degree of circularity, i.e., roundness, can be calculated by 4π × (alloy area) ÷ (circumference). 2 Definition. The edges of copper-tin alloy particles were extracted from the acquired secondary electron image using the well-known image processing software ImageJ (ver. 1.54f), and the alloy area and perimeter were calculated. This was achieved by averaging the roundness of at least 10 copper-tin alloy particles obtained from a single secondary electron image.

[0121] (Exposed area ratio of copper-tin alloy layer on the surface of tin layer)

[0122] The measurement section was set as section A, and a 0.0028 mm sample was observed at 2000x magnification using a SEM (Scanning Electron Microscope) (JEOL Ltd. JSM-7001F). 2 The reflected electron image of the field of view. The backscattered electron image obtained above was binarized using the well-known image processing software ImageJ (ver. 1.54f), so that the exposed Cu-Sn alloy layer on the surface was black and the Sn layer was white. The exposed area ratio was calculated by determining the area of ​​the Cu-Sn alloy layer. The binarization was performed at 112 of the grayscale range of 255.

[0123] (Wear amount)

[0124] Each sample was cut into 60mm long pieces parallel to the rolling direction, which were used as male terminals (male terminal samples). Furthermore, the samples used as female terminals were all identical, produced by cutting unprocessed sample 31 from Table 3 into 60mm × 10mm pieces, and embossing a 2.5mm radius of curvature in the center of the sample. The test was conducted using a friction and wear testing machine (UMT-Tribolab) manufactured by Bruker AXS KK. The convex surface of the female terminal sample and the sliding portion of the horizontally positioned male terminal sample... Figure 1 The male terminal sample was brought into contact with part A, and a load of 1 N was applied while it was slid back and forth 500 times, covering a distance of 1 mm. During the measurement, the sliding marks of the male terminal sample were observed at 20x magnification along the depth direction in a direction perpendicular to the sliding motion using a white interference microscope (NexView 8300 manufactured by AMETEK Co., Ltd). Regarding the wear amount, the cross-sectional wear area at the deepest wear location was derived, and this area was less than 300 μm. 2 Let's call the case A, and set 300μm 2 Above and 1200μm 2 The following case is set as B, which will exceed 1200μm. 2 Let's assume the case is C.

[0125] (Coefficient of friction)

[0126] Each sample was cut into 60mm long pieces parallel to the rolling direction, which were used as male terminals (male terminal test pieces). Furthermore, the female terminals were all identical, produced by cutting unprocessed sample 31 from Table 3 into 60mm × 10mm pieces, and embossing a 2.5mm radius of curvature in the center of the test piece. The coefficient of friction of these test pieces was measured. During the measurement, a friction and wear testing machine (UMT-Tribolab) manufactured by Bruker AXS KK was used to represent the horizontally positioned male terminal test pieces. Figure 1 With part A at the center of the sliding part, the convex surface of the female terminal test piece contacts a position 5mm below part A. While applying a load of 5N to the male terminal test piece, it slides 10mm until it reaches a position 5mm above part A. Friction coefficient data is obtained for every 0.013mm sliding distance, and the average friction coefficient obtained over distances from 0.1mm to 10mm is taken as the friction coefficient value.

[0127] (Contact resistance)

[0128] Test pieces were prepared in the same manner as those for friction coefficient testing, with an embossed radius of curvature of 1.5 mm. After heating these at 150°C for 250 hours, the contact resistance (mΩ) was measured. During the measurement, a Bruker AXS KK tribolab (UMT-Tribolab) was used. The convex surface of the female terminal test piece was brought into contact with a horizontally positioned male terminal test piece, and the contact resistance was measured using the 4-terminal method when a 5 N load was applied to the male terminal test piece.

[0129] Furthermore, the coefficient of friction, wear amount, and contact resistance were not evaluated for materials that developed cracks during indentation.

[0130] These measurement results are shown in Table 3.

[0131] [Table 3]

[0132]

[0133] The friction coefficient, wear amount, and contact resistance of samples 1–30 were all low and good. Among these samples, the average thickness of the nickel layer was ≥0.05 μm and ≤3.00 μm, the average thickness of the tin layer was ≥0.05 μm and ≤2.00 μm, and the average thickness of the copper-tin alloy layer was ≥0.15 μm and ≤1.55 μm. The arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer was ≥700 mm. -1 Above and 2200mm -1 Within the following range.

[0134] Among these, samples 4 and 19 had a roundness of less than 0.5 compared to the others, resulting in slightly more wear. The exposed area ratio of the copper-tin alloy layer in sample 19 exceeded the specified range. This is presumably due to the longer cooling time required to reduce the temperature of the plated substrate to 50°C during the reflow soldering process. In samples 28-30, the average thickness of the tin layer was greater than in the other samples, thus resulting in a smaller exposed area ratio of the copper-tin alloy layer.

[0135] Figure 5 This is a backscattered electron (BSE) image of the cross-section of sample 3. It can be seen that a copper-tin alloy layer with an uneven surface is formed on the nickel layer, and a tin layer is formed on top of it. Furthermore, it is confirmed that the copper-tin alloy layer consists of a Cu3Sn layer formed by slight dispersion on the nickel layer and a Cu6Sn5 layer formed in a manner that covers the area above the Cu3Sn layer and the area above the nickel layer where no Cu3Sn layer exists.

[0136] For these samples, sample 31 had an average tin layer thickness within the specified range, but a high Spc and significant wear. This is presumably due to the high temperature in the first furnace during the reflow soldering process. Samples 32 and 37 had excessively thin copper-tin alloy layers, making it impossible to determine their Spc and roundness; they also exhibited high friction coefficients and significant wear. This is likely due to the absence of either the first or second heat treatment process during the reflow soldering process.

[0137] In samples 33 and 34, the copper-tin alloy layer was thin and the Spc was small, resulting in a high coefficient of friction and significant wear. This is presumably due to insufficient initial heat treatment during the reflow soldering process.

[0138] In sample 35, the Spc was large and the wear was increased due to the excessively high temperatures in the first and second reflow ovens during the reflow soldering process. Furthermore, the contact resistance was high due to the thin solder layer.

[0139] In sample 36, the solder layer became thin and the contact resistance was high because the first heating treatment in the reflow soldering process took too long.

[0140] Samples 38 and 39 had low Spc values, resulting in high friction coefficients and significant wear. This is presumably due to insufficient second heating treatment during the reflow soldering process.

[0141] The second furnace temperature during the reflow soldering process of sample 40 was too high, resulting in a large Spc and reduced abrasion resistance. On the other hand, the contact resistance was high due to the thin solder layer.

[0142] In sample 41, the tin layer became thin and the contact resistance was high because the second heating treatment time during the reflow soldering process was too long.

[0143] In sample 42, the tin plating layer was too thick, resulting in a thicker tin layer and a higher coefficient of friction.

[0144] Samples 43 and 44 also had residual copper plating after the reflow soldering process.

[0145] In sample 43, the copper plating layer met the specified thickness, but the tin plating layer did not. Therefore, the exposed area ratio after reflow soldering was larger than specified, the Spc (spc) was smaller, and thus the wear was greater. Furthermore, due to the thin tin layer, the contact resistance was high. Conversely, in sample 44, the copper plating layer thickness was thicker than specified. Therefore, the average thickness of the copper-tin alloy layer after reflow soldering was thicker than specified, the tin layer was thinner, and thus the exposed area ratio was larger than specified. Furthermore, copper plating residue was observed after reflow soldering, and the shape of the copper-tin alloy layer became flatter, resulting in a slightly smaller Spc, falling within the specified range. Therefore, the wear was slightly greater. Furthermore, due to the thin tin layer, the contact resistance was high.

[0146] In sample 45, the thickness of the copper plating layer and the average thickness of the copper-tin alloy layer are thinner than the specified range. Therefore, part of the copper-tin alloy is replaced by nickel, the shape of the copper-tin alloy becomes steeper, and the Spc is greater than the specified range. As a result, the coefficient of friction becomes higher and the amount of wear is greater.

[0147] The nickel layer on sample 46 was too thick, which caused cracks during indentation. The coefficient of friction, wear, and contact resistance were not evaluated.

[0148] In sample 47, the contact resistance was high because the nickel layer was too thin.

[0149] In sample 48, because the first and second heating treatments during reflow soldering were at the same temperature, the copper-tin alloy layer did not form the specified shape, the Spc was less than the specified range, and the wear was excessive.

[0150] Regarding sample 49, because the temperature of the second heating treatment during reflow soldering was lower than that of the first heating treatment, the copper-tin alloy layer did not achieve the specified shape, the Spc was less than the specified range, and the wear was excessive.

[0151] Next, by arbitrarily combining the above samples, the Spc and roundness difference of the copper-tin alloy layer were determined, and the coefficient of friction was measured. In this case, one was designated as the male terminal and the other as the female terminal, and the coefficient of friction was measured using the same method as described above.

[0152] The results are shown in Table 4.

[0153] [Table 4]

[0154]

[0155] It exhibits a good coefficient of friction regardless of the combination, but the difference in Spc between the male and female terminals is 200 mm. -1 Above and 1200mm -1 Among the samples 53 to 62 below, a particularly good coefficient of friction was observed. The roundness difference was all below 0.4. It is speculated that due to the moderate difference in the shape of the copper-tin alloy layer, the contact point of the copper-tin alloy layer becomes smaller during sliding, the actual contact area becomes smaller, and therefore the sliding marks become smaller. In addition, the male and female terminals of sample 52 are both within the scope of the present invention, but the difference in Spc is less than 200 mm. -1 Therefore, the coefficient of friction becomes slightly higher.

[0156] The Spc of single-sided terminals of samples 55, 56, 59, and 60 exceeds 2200mm. -1 However, the Spc of the other terminal is appropriate, thus resulting in a low coefficient of friction.

[0157] On the other hand, the Spc of both the male and female terminals of sample 51 exceeds 2200mm. -1 The coefficient of friction is high. The difference in Spc between the female and male terminals exceeds 1200 mm. -1 In samples 63 and 64, the coefficient of friction showed a slightly higher value. This is presumably because the copper-tin alloy layer of the other terminal has a finer texture compared to the texture of the copper-tin alloy layer on the other terminal, which could cause it to break during sliding.

[0158] Industrial availability

[0159] According to the present invention, vehicle-mounted connectors and the like used in electrical wiring connections for automobiles and the like can be utilized.

[0160] Symbol Explanation

[0161] 1. Connector terminal materials

[0162] 10 terminal section

[0163] 11 and 12 connecting parts

[0164] 13 Connecting parts

[0165] 14 Shoulders

[0166] 15Substrate fixing part

[0167] 21 substrate

[0168] 22 membranes

[0169] 23 nickel layers

[0170] 24 Copper-Tin Alloy Layer

[0171] 25 tin layers

[0172] 31 Nickel plating

[0173] 32 copper plating layer

[0174] 33 Tin plating layer

[0175] 35 substrates with coating

Claims

1. A terminal material for a connector, characterized in that, A film is formed on the surface of a substrate made of copper or a copper alloy, and the film comprises: a nickel layer formed on the surface of the substrate and made of nickel or a nickel alloy; a copper-tin alloy layer formed on the nickel layer and made of an alloy of copper and tin; and a tin layer formed on the copper-tin alloy layer and made of tin or a tin alloy. A portion of the copper-tin alloy layer is exposed on the surface of the tin layer. The average thickness of the nickel layer is greater than 0.05 μm and less than 3.00 μm. The arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer, measured after the tin layer was removed to expose the copper-tin alloy layer, was 700 mm. -1 Above and 2200mm -1 Hereinafter, the average thickness of the tin layer is 0.05 μm or more and 2.00 μm or less, and the average thickness of the copper-tin alloy layer is 0.15 μm or more and 1.55 μm or less.

2. The connector terminal material according to claim 1, characterized in that, The roundness of the copper-tin alloy particles on the surface of the copper-tin alloy layer, measured after the tin layer of the coating is removed to expose the copper-tin alloy layer, is 0.5 or higher.

3. The connector terminal material according to claim 1 or 2, characterized in that, The exposed area of ​​the copper-tin alloy layer on the surface of the tin layer is more than 5% and less than 70%.

4. The connector terminal material according to claim 1 or 2, characterized in that, It has a connecting portion that connects to the opposite side and a substrate fixing portion that is fixed to the substrate, and the coating is formed at least in the connecting portion.

5. The connector terminal material according to claim 4, characterized in that, A tin surface layer composed of tin or a tin alloy is formed on the entire surface of the front, back and both sides of the substrate fixing part.

6. A connector, characterized in that, It has one side terminal and another side terminal that can be interconnected, at least one of these one side terminal and the other side terminal being made of the connector terminal material as described in claim 1 or 2, and the difference in the arithmetic mean curvature Spc of the peak vertices on the surfaces of the copper-tin alloy layers of the one side terminal and the other side terminal is within 200 mm. -1 Above and 1200mm -1 Within the following range.

7. The connector according to claim 6, characterized in that, The difference in roundness of the copper-tin alloy particles on the surface of the copper-tin alloy layer of the terminal on one side and the terminal on the other side is within the range of less than 0.

4.

8. A method for manufacturing a connector terminal material, characterized in that, include: The plating layer formation process involves sequentially stacking 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) on the surface of a substrate made of copper or a copper alloy, thereby forming a plating-coated substrate; and a reflow soldering process, which involves heating the plating-coated substrate using a reflow soldering process. In the plating layer formation process, the thickness of the nickel plating layer is formed to be 0.05 μm or more and 3.00 μm or less, the thickness of the copper plating layer is formed to be 0.10 μm or more and 0.70 μm or less, and the thickness of the tin plating layer is formed to be 0.20 μm or more and 2.90 μm or less. The reflow soldering process includes: a first heating treatment, in which the substrate with the plating layer is passed through a first heating furnace at a first furnace temperature set between 150°C and 270°C in an atmospheric atmosphere for a period of 3 seconds to 30 seconds, heating the substrate with the plating layer to a temperature lower than the melting point of tin; a second heating treatment, in which, after the first heating treatment, the substrate with the plating layer is passed through a second heating furnace at a second furnace temperature set between 232°C and 350°C, which is higher than the first furnace temperature, for a period of 3 seconds to 35 seconds; and a cooling treatment, in which the substrate with the plating layer is rapidly cooled immediately after the tin plating layer has melted in the second heating treatment. In the cooling process, the cooling time until the temperature of the substrate with the coating reaches 50°C is set to be more than 4 seconds and less than 60 seconds.

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