Terminal material for connector, method for manufacturing same, and connector

Abstract

In the present invention, a coating film is formed on a surface of a substrate made of copper or a copper alloy. The coating film comprises: a nickel layer that is composed of nickel or a nickel alloy and is formed on the surface of the substrate; a copper-tin alloy layer that is composed of an alloy of copper and tin and is formed on the nickel layer; and a tin layer that is composed of tin or a tin alloy and is formed on the copper-tin alloy layer. The average thickness of the nickel layer is 0.05 μm to 3.00 μm, the arithmetic mean peak curvature Spc of the surface of the copper-tin alloy layer is 700 mm-1 to 2200 mm-1, the average thickness of the tin layer is 0.05 μm to 2.00 μm, and the average thickness of the copper-tin alloy layer is 0.15 μm to 1.55 μm.

Description

Connector terminal material, manufacturing method thereof, and connector

[0001] The present invention relates to a terminal material for a connector having a reduced coefficient of friction on the surface of the terminal material, 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 Japanese Patent Application No. 2024-154278 filed on September 6, 2024, the contents of which are incorporated herein by reference.

[0003] Conventionally, there are known automotive connectors used for connecting electrical wiring in automobiles, etc. The automotive connector (automotive terminal) includes a terminal pair designed to be electrically connected by contacting a contact piece provided on the female terminal with a male terminal inserted into the female terminal at a predetermined contact pressure.

[0004] As such a connector (terminal), a terminal material with excellent wear resistance is known, which is formed by copper plating and tin plating on a copper or copper alloy plate and then performing a reflow process to form a copper-tin alloy layer and a tin layer on the copper or copper alloy plate.

[0005] As a terminal material having such a copper-tin alloy layer and a tin layer, for example, in Patent Document 1, the roughness of the substrate is controlled to control the state of exposure of the copper-tin alloy layer from the tin layer, thereby reducing the insertion force; however, it is necessary to process the substrate in advance to control the roughness.

[0006] In addition, in Patent Document 2, the insertion force is reduced by making the tin layer made of tin or a tin alloy on the copper-tin alloy layer very thin, but there is a problem in that the contact resistance after heating increases because the tin layer is small.

[0007] Furthermore, in Patent Document 3, a part of the copper-tin alloy is replaced with nickel (Ni) to give the copper-tin alloy a steeply uneven shape, and a tin layer of 0.2 μm to 0.6 μm is left, thereby reducing friction and preventing an increase in contact resistance during heating. However, because the copper-tin alloy layer is steep, it is easily scraped during sliding, which causes problems such as poor wear resistance.

[0008] JP 2007-100220 A JP 2011-012320 A JP 2014-240520 A

[0009] In the terminal materials described in these patent documents, in order to reduce the coefficient of friction, the tin layer on the surface is made thin and the proportion of the hard copper-tin alloy layer is increased. Since the soft tin layer on the surface is prone to adhesion during insertion and removal, there is a problem that the insertion force is high. To prevent this adhesion, it is advisable to expose the copper-tin alloy layer on the outermost surface, but this increases contact resistance in high-temperature environments and lacks wear resistance against fretting wear.

[0010] The present invention has been made in view of the above circumstances, and has as its object to control the surface shape of a copper-tin alloy layer, reduce the coefficient of friction, and improve the wear resistance and heat resistance.

[0011] The terminal material for a connector of the present invention has a coating formed on the surface of a substrate made of copper or a copper alloy, and the coating has a nickel layer made of nickel or a nickel alloy formed on the surface of the substrate, a copper-tin alloy layer made of an alloy of copper and tin formed on the nickel layer, and a tin layer made of tin or a tin alloy formed on the copper-tin alloy layer, 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 Over 2200mm －１ 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.

[0012] The smaller the arithmetic mean curvature Spc of the peak, the more rounded the tip is, and the larger it is, the more pointed the tip is. －１ If the arithmetic mean curvature Spc of the peaks is less than 2200 mm, the surface shape of the copper-tin alloy layer (the shape of the interface with the tin layer) becomes gentle, and the contact area with the mating terminal increases, resulting in a high coefficient of friction. Also, the wear resistance decreases. －１ If the thickness exceeds 1000 nm, the surface shape of the copper-tin alloy layer becomes sharper, which makes the copper-tin alloy layer more susceptible to abrasion during sliding, resulting in an increase in the coefficient of friction and a decrease in wear resistance.

[0013] In this case, if the average thickness of the tin layer is less than 0.05 μm, the contact resistance in a high temperature environment increases, and if it exceeds 2.00 μm, adhesive wear is likely to occur during sliding, and the coefficient of friction increases.

[0014] Furthermore, when the average thickness of the copper-tin alloy layer is less than 0.15 μm, the arithmetic mean curvature Spc of the peaks becomes small, resulting in a high coefficient of friction and a decrease in wear resistance.When the average thickness of the copper-tin alloy layer is more than 1.55 μm, the arithmetic mean curvature Spc of the peaks becomes large, resulting in a high coefficient of friction and a decrease in wear resistance.

[0015] The nickel layer has the effect of preventing copper diffusion from the substrate in a high-temperature environment, but if the average thickness is less than 0.05 μm, the effect of preventing copper diffusion from the substrate is poor, the rate at which copper turns into a copper-tin alloy increases, and the contact resistance increases. If the average thickness of the nickel layer exceeds 3.00 μm, cracks may occur during bending.

[0016] In the terminal material for connectors of the present invention, the copper-tin alloy particles on the surface of the copper-tin alloy layer may have a circularity of 0.5 or more.

[0017] The closer the circularity is to 1, the closer it is to a perfect circle, the more stable the contact point is, and a good coefficient of friction can be obtained. If the circularity is less than 0.5, the function as the contact point becomes uneven, the coefficient of friction becomes slightly high, and the wear resistance decreases slightly.

[0018] In the terminal material for connectors 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, and 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.

[0019] The copper-tin alloy layer, which is harder than the tin layer, is exposed on the surface, and this, combined with the lubricating effect of the soft tin layer, reduces the coefficient of friction. If the exposed area ratio of this copper-tin alloy layer is less than 5%, the effect of reducing the coefficient of friction is poor, and if the exposed area ratio exceeds 70%, the area occupied by the tin layer on the surface becomes small, which may increase contact resistance in high-temperature environments.

[0020] The terminal material for a connector of the present invention preferably has a connecting portion to be connected to a mating part and a board fixing portion to be fixed to a board, and at least the connecting portion is coated with the coating.

[0021] In this case, it is preferable that the substrate fixing portion has a tin surface layer made of tin or a tin alloy formed on the entire front, back and both side surfaces.

[0022] The formation of the above-mentioned coating at least on the connection portion results in a terminal with excellent insertability. Furthermore, in a terminal material for a connector that needs to be fixed to a board, it is preferable to use a "post-plating method" in which plating is performed after punching a metal plate, and it is preferable that the above-mentioned coating is formed at least on the connection portion that will be connected to the mating side, and that a tin surface layer made of tin or a tin alloy is formed on the entire surface of at least the portion that is fixed to the board.

[0023] In the case of pin-shaped terminals, a tin surface layer made of tin or a tin alloy is formed on the entire surface of the board fixing part, which gives the terminal excellent solderability, and the formation of the above-mentioned coating at the connection part with the mating part makes the terminal also excellent in insertability.

[0024] The connector of the present invention has one terminal and another terminal that are connectable to each other, at least one of the one terminal and the other terminal is made of the connector terminal material, and the difference in arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer of the one terminal and the other terminal is 200 mm －１ Over 1200mm －１ The following range is preferable.

[0025] The difference in arithmetic mean curvature Spc of the peak is 200 mm －１ Over 1200mm －１ By setting the range below, the real contact area is reduced, which reduces the sliding trace and further reduces the coefficient of friction.

[0026] Furthermore, if the difference in circularity of the copper-tin alloy particles on the surface of the copper-tin alloy layer between the one terminal and the other terminal is in the range of 0.4 or less, the coefficient of friction can be further reduced.

[0027] The method for manufacturing a terminal material for a connector of the present invention includes a plating layer forming step of laminating a nickel plating layer made of nickel or a nickel alloy, a copper plating layer made of copper or a copper alloy, and a tin plating layer made of tin or a tin alloy in this order on the surface of a substrate made of copper or a copper alloy to form a substrate with a plating layer, and a reflow treatment step of performing a reflow treatment of heating the substrate with a plating layer, wherein in the plating layer forming step, the thickness of the nickel plating layer is 0.05 μm or more and 3.00 μm or less, the thickness of the copper plating layer is 0.10 μm or more and 0.70 μm or less, and the thickness of the tin plating layer is 0.20 μm or more and 2.90 μm or less. The reflow treatment process includes a first heating treatment in which the base material with the plating layer is passed through a first heating furnace set to a first furnace temperature of 150°C or more and 270°C or less in an air atmosphere for a time of 3 seconds or more and 30 seconds or less to heat the base material with the plating layer to a temperature below the melting point of tin; a second heating treatment in which, after the first heating treatment, the base material with the plating layer is passed through a second heating furnace set to a second furnace temperature of 232°C or more and 350°C or less for a time of 3 seconds or more and 35 seconds or less to heat the base material with the plating layer; and a cooling treatment in which the base material with the plating layer is rapidly cooled immediately after the tin plating layer is melted by the second heating treatment.

[0028] By performing the reflow treatment process as a two-stage heating process under predetermined temperature conditions and then cooling, the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer can be controlled within a predetermined range. In this case, the copper-tin alloy is grown in the first heating process, and then melted in the second heating process to form a copper-tin alloy layer of a predetermined shape. Therefore, the temperature of the second heating process must be higher than that of the first heating process. If the first heating process and the second heating process are performed at the same temperature, or if the temperature of the second heating process is lower than that of the first heating process, the copper-tin alloy layer cannot be formed into the predetermined shape, and it becomes difficult to control the arithmetic mean curvature Spc of the peaks on the surface within a predetermined range. Note that although the plating layer changes during the reflow treatment process, the substrate is referred to as a substrate with a plating layer until the reflow treatment process is completed.

[0029] If the heating in the reflow treatment is insufficient, the average thickness of the copper-tin alloy layer will be less than 0.15 μm, and if the heating in the reflow treatment is excessive, the average thickness of the copper-tin alloy layer will exceed 1.55 μm.

[0030] In the first heat treatment of this reflow process, the substrate with the plating layer is heated to a temperature below the melting point of tin without melting the tin plating layer. In the second heat treatment, the tin plating layer on the outermost surface is melted and brightened, and then the substrate is immediately cooled. Therefore, in this second heat treatment, the substrate with the plating layer is always in an elevated temperature state and is not maintained at the peak temperature at which tin melts.

[0031] Here, the shape of the copper-tin alloy layer is affected not only by the reflow treatment 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 thickness of the copper plating layer is 0.10 μm or more but less than 0.20 μm, the copper plating layer remains, the Spc decreases, the friction coefficient increases, and the wear resistance decreases. Furthermore, the thin tin layer increases the contact resistance. When the thickness of the copper plating layer is less than 0.10 μm, part of the copper-tin alloy is replaced by nickel, resulting in a steep shape of the copper-tin alloy layer, a large Spc, a high friction coefficient, and a decrease in wear resistance.

[0032] In the cooling treatment, the cooling time until the temperature of the base material with a plating layer reaches 50° C. is preferably 4 seconds or more and 60 seconds or less.

[0033] According to the present invention, by controlling the surface of the copper-tin alloy layer to a predetermined shape, it is possible to reduce the coefficient of friction and improve the wear resistance and heat resistance.

[0034] Fig. 2 is a plan view of a connector terminal material according to an embodiment of the present invention; Fig. 3 is a schematic cross-sectional view of the connector terminal material of Fig. 1; Fig. 4 is a flowchart showing a method for manufacturing the connector terminal material of Fig. 1; Fig. 5 is a schematic cross-sectional view showing a substrate with a plating layer before the reflow treatment process of the connector terminal material of Fig. 2; Fig. 6 is a backscattered electron (BSE) image of a cross section of sample 7;

[0035] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0036] [Configuration of terminal material for connector] As shown in Figure 1, the terminal material for connector 1 of this embodiment is a terminal chain formed by connecting multiple terminal portions 10 in the shape of pin terminals, and is formed by punching out a long plate material using a press process.

[0037] Specifically, a plurality of terminal portions 10 are provided in parallel between a pair of elongated connecting members 11, 12 along the direction connecting the two connecting members 11, 12. Each terminal portion 10 has a pin-shaped connecting portion 13, a wide shoulder portion 14, and a board fixing portion 15 formed continuously from the tip, and both ends (the tip of the connecting portion 13 and the base end of the board fixing portion 15) are connected to the connecting members 11, 12, respectively. This terminal portion 10 is used by being fixed in an electrically connected state to a board or the like by press-fitting or soldering the board fixing portion 15 into a through-hole or the like of the board, and electrical connection is made by inserting the connecting portion 13 into another female terminal.

[0038] The shape of the terminal is merely an example and is not limited to that shown in FIG. 1, and may be any shape having a connecting portion for electrical connection with a mating terminal.

[0039] As shown in the cross section of Figure 2, this connector terminal material 1 has a coating 22 formed on a substrate 21 made of copper or a copper alloy, and the coating 22 is made up of a nickel layer 23 made of nickel or a nickel alloy, a copper-tin alloy layer 24 made of an alloy of copper and tin, and a tin layer 25 made of tin or a tin alloy, which are formed in this order.

[0040] FIG. 2 shows a cross section in the thickness direction, and the coating 22 is formed on the entire surface of both the front and rear surfaces and both side surfaces of the substrate 21 .

[0041] The composition of the substrate 21 is not particularly limited as long as it is made of copper or a copper alloy, and it may be made of, for example, a plate material made of copper or a copper alloy such as oxygen-free copper (C10200), a Cu-Mg copper alloy (C18665), brass, or phosphor bronze.

[0042] The nickel layer 23 functions to suppress copper diffusion from the substrate 21 into the copper-tin alloy layer 24 and the tin layer 25 formed thereon. 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 nickel layer 23 is less effective at preventing copper diffusion from the substrate 21 in high-temperature environments, and the rate at which the nickel layer becomes a copper-tin alloy increases, resulting in high contact resistance. On the other hand, if the average thickness of the nickel layer 23 exceeds 3.00 μm, cracks may occur during bending. The composition of the nickel layer 23 is not particularly limited as long as it is made of nickel or a nickel alloy. The average thickness of the nickel layer 23 is preferably 0.10 μm or more and 2.00 μm or less.

[0043] The copper-tin alloy layer 24 is a layer obtained by sequentially forming a copper plating layer and a tin plating layer on the nickel layer 23 and then performing a reflow treatment. The surface of this copper-tin alloy layer 24, i.e., the interface with the overlying tin layer 25, is formed with an uneven shape, and a portion of this uneven shape is exposed on the surface of the tin layer 25. The average thickness of this copper-tin alloy layer 24 is 0.15 μm or more and 1.55 μm or less. The average thickness of this 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 treatment conditions described below and the thicknesses of the tin plating layer 33 and the copper plating layer 32 during manufacturing.

[0044] Regarding the influence of the reflow treatment conditions, first, if the average thickness of the copper-tin alloy layer 24 is less than 0.15 μm due to insufficient heating during the reflow treatment, the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24, which will be described later, becomes small, the exposed area ratio on the surface of the tin layer 25 decreases, and the coefficient of friction increases. Furthermore, the hard copper-tin alloy layer 24 has a small average thickness, which reduces wear resistance. On the other hand, if the average thickness of the copper-tin alloy layer 24 exceeds 1.55 μm due to excessive heating during the reflow treatment, 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 the wear resistance decreases. The lower limit of the average thickness of the copper-tin alloy layer 24 is preferably 0.31 μm.

[0045] The influence of the thickness of the tin plating layer 33 and the copper plating layer 32 during manufacturing is as follows: First, the thickness of the copper plating layer is 0.10 μm or more. If the thickness of the tin plating layer is less than 0.20 μm, the copper plating layer remains, the SPC decreases, the friction coefficient increases, and the wear resistance decreases. Furthermore, the thin tin layer increases the contact resistance. On the other hand, if the thickness of the copper plating layer is less than 0.10 μm, part of the copper-tin alloy is replaced by nickel, resulting in a steep shape of the copper-tin alloy layer, a large SPC, a high friction coefficient, and a decrease in wear resistance.

[0046] 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. The copper-tin alloy layer 24, which is harder than the tin layer 25, is exposed on the surface, which, combined with the lubricating effect of the soft tin layer 25, reduces the coefficient of friction. If the exposed area ratio of the copper-tin alloy layer 24 is less than 5%, the effect of reducing the coefficient of friction is poor, and the surface area of ​​the tin layer 25 increases accordingly, which may make adhesive wear more likely to occur and increase the coefficient of friction. Furthermore, wear resistance may also decrease. If the exposed area ratio exceeds 70%, the area occupied by the tin layer 25 on the surface may become smaller, which may increase contact resistance in high-temperature environments. It is more preferable that the exposed area ratio of the copper-tin alloy layer 24 be 10% or more and 50% or less.

[0047] In addition, 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 was 700 mm －１ Over 2200mm －１ The arithmetic mean curvature Spc of the peak is a parameter measured in accordance with ISO 25178, and the smaller this value, the more rounded the tip is, and the larger this value, the more pointed the tip is. －１ If the thickness is less than 1000 nm, the surface shape of the copper-tin alloy layer 24 (the shape of the interface with the tin layer 25) becomes gentle. Also, the exposed area ratio decreases, and the area occupied by the tin layer 25 on the surface of the coating 22 tends to increase accordingly. As a result, the coefficient of friction increases and the wear resistance decreases.

[0048] On the other hand, the arithmetic mean curvature Spc of the peak is 2200 mm －１If the surface shape of the copper-tin alloy layer 24 exceeds 900 mm, the copper-tin alloy layer 24 becomes sharper, so that the copper-tin alloy layer 24 is more likely to be scraped during sliding, and the coefficient of friction increases. Also, the wear resistance decreases. The arithmetic mean curvature Spc of the peaks on the surface of this copper-tin alloy layer 24 is 900 mm. －１ Over 1900mm －１ The following is preferred:

[0049] Furthermore, the degree of circularity 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 more. This degree of circularity is calculated by the following formula: 4π × (particle area) ÷ (perimeter) ２ The closer the circularity of the copper-tin alloy particles is to 1, the closer they are to a perfect circle, and since they are arranged in a state that is close to a circle when viewed from the surface, they are stable as contact points and can achieve a low coefficient of friction.

[0050] If the circularity of the copper-tin alloy particles is less than 0.5, the copper-tin alloy layer 24 exposed on the surface of the tin layer 25 during sliding as a connector may have uneven contact with the mating terminal, resulting in a high coefficient of friction. Furthermore, wear resistance is slightly reduced. The circularity of the copper-tin alloy particles is more preferably 0.55 or more. The higher the circularity of the copper-tin alloy particles, the lower the coefficient of friction and the better the results. However, it is practically difficult to control the shape of the copper-tin alloy layer 24 to a circularity of more than 0.85.

[0051] The tin layer 25 is a layer made of tin or a tin alloy, and is formed with an average thickness of 0.05 μm or more and 2.00 μm or less. If the average thickness of this tin layer is less than 0.05 μm, contact resistance in high-temperature environments increases, while if it exceeds 2.00 μm, adhesive wear is more likely to occur and the friction coefficient increases. The exposed area ratio of the copper-tin alloy layer 24 also decreases. The average thickness of this 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.

[0052] [Manufacturing Method of Connector Terminal Material] Next, a method for manufacturing the connector terminal material 1 will be described. As shown in Fig. 3, the manufacturing method of the connector terminal material 1 includes a punching step in which a long, narrow plate material is punched by a press to form a chain of terminals that will become the substrate 21, a pretreatment step in which the surface of the substrate 21 after punching is cleaned, a plating layer forming step in which a nickel plating layer 31, a copper plating layer 32, and a tin plating layer 33 are formed in that order on the surface of the substrate 21, and a reflow treatment step in which the plated-layer-coated substrate 35 on which the three plating layers 31 to 33 have been formed is heated and reflow-treated. The steps will be described below in order.

[0053] (Punching Process) The elongated plate material wound in a coil shape is punched out by a press while being unwound, to form a chained-terminals body that will become the base material 21 as shown in FIG.

[0054] (Pretreatment Step) The base material 21 after punching is subjected to pretreatment such as degreasing and pickling to clean the surface.

[0055] (Plating Layer Forming Step) - Nickel Plating Layer - The surface of the pretreated substrate 21 is subjected to a nickel plating treatment to form a nickel plating layer 31 made of nickel or a nickel alloy. A typical nickel plating bath may be used, for example, a sulfamate bath containing nickel sulfamate, nickel chloride, or boric acid as its main components. The plating bath temperature is 40°C or higher and 60°C or lower, and the current density is 1 A / dm ２ 10A / dm or more ２ The thickness of the nickel plating layer 31 is set to be 0.05 μm or more and 3.00 μm or less.

[0056] - Copper plating layer - A copper plating process is carried out on the nickel plating layer 31 to form a copper plating layer 32 made of copper or a copper alloy. A common copper plating bath may be used for the copper plating, such as a copper sulfate bath containing copper sulfate and sulfuric acid as its main components. The temperature of the plating bath is 20°C to 60°C, and the current density is 1 A / dm ２ 10A / dm or more ２ The following is said to be true.

[0057] The thickness of this copper plating layer 32 is 0.10 μm or more and 0.70 μm or less. If the thickness of the copper plating layer is 0.10 μm or more but the thickness of the tin plating layer is less than 0.20 μm, the copper plating layer remains after the reflow treatment process, the SPC is reduced, the coefficient of friction is increased, and the wear resistance is reduced. 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 treatment process is increased, which may result in high contact resistance. On the other hand, if the thickness of the copper plating layer 32 is less than 0.10 μm, part of the copper-tin alloy is replaced by nickel, which may result in a steep shape of the copper-tin alloy layer, a large SPC, a high coefficient of friction, and reduced wear resistance. There is also a risk of the exposed area ratio of the copper-tin alloy layer 24 being reduced. The thickness of this 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.

[0058] - Tin plating layer - A tin plating process is carried out on the copper plating layer 32 to form a tin plating layer 33 made of tin or a tin alloy. A general tin plating bath may be used as the plating bath for forming the tin plating layer 33, and for example, a methanesulfonic acid bath containing methanesulfonic acid and tin methanesulfonate as the main components may 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 / dm ２ 20A / dm or more ２ The following is said to be true.

[0059] The thickness of this tin plating layer 33 is set to 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 treatment process will be thin, which may increase contact resistance in high-temperature environments. If the thickness of the tin plating layer 33 exceeds 2.90 μm, the tin layer 25 after the reflow treatment process will be thick, the exposed area ratio of the copper-tin alloy layer 24 will be reduced, adhesive wear will be more likely to occur, and the friction coefficient may increase. The thickness of this 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.

[0060] By forming the nickel plating layer 31, copper plating layer 32, and tin plating layer 33 in this order on the surface of the substrate 21, a substrate 35 with plated layers, in which three plating layers 31 to 33 are laminated, is obtained, as shown in Figure 4. In this case, the substrate 21 before plating is in a state where it has been punched into a chain terminal shape by a press, and the substrate 21 is immersed in a plating bath to form the plating layers 31 to 33, so that the three plating layers 31 to 33 are formed not only on the front and back surfaces of the substrate 21 but also on both side surfaces (the cut end surfaces during punching). However, the present invention can also be used in a "partial plating" process in which only a portion of the substrate is immersed in a plating bath.

[0061] (Reflow Treatment Step) The plated layer-equipped substrate 35 having the plated layers 31 to 33 formed thereon as described above is subjected to a reflow treatment. In this reflow treatment step, in the case of a long, narrow plate material (strip material) wound on a roll, the plate material is run in the lengthwise direction and passed through a reflow furnace while the above-described pretreatment and plating treatment are continuously performed. However, in the case of the plated layer-equipped substrate 35 of this embodiment, it is a punched material that has been punched out in advance by a press into a chain of terminals of a predetermined length as shown in FIG. 1 , and after the above-described pretreatment and plating treatment are performed on this punched material, the plated layer-equipped substrate 35 is supplied to a relatively small reflow furnace and subjected to the reflow treatment.

[0062] Specifically, the process includes a first heating treatment in which the plated layer-attached substrate 35 is passed through a first heating furnace set to a first furnace temperature of 150°C or more and 270°C or less in an air atmosphere for a time period of 3 seconds or more and 30 seconds or less to heat the substrate 35 to a temperature below the melting point of tin; a second heating treatment in which the plated layer-attached substrate 35 is passed through a second heating furnace set to a second furnace temperature of 232°C or more and 350°C or less, which is higher than the first furnace temperature, for a time period of 3 seconds or more and 35 seconds or less; and a cooling treatment in which the plated layer-attached substrate 35 is rapidly cooled immediately after the tin plating layer has been melted by the second heating treatment.

[0063] In this reflow treatment step, a two-stage heating process is performed in which the tin plating layer 33 is heated to just below the melting temperature, and then the tin plating layer 33 is further reflowed and melted, thereby allowing 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 circularity of the peaks on the surface of the copper-tin alloy layer 24 to be controlled within a predetermined range.

[0064] The atmosphere for the first and second heat treatments in this reflow treatment step may be air, and water vapor may be additionally introduced.

[0065] In this case, in the first heating treatment, the temperature inside the furnace may be as high as 270°C, for example, but the temperature of the plated substrate 35 does not rise to the melting temperature of tin, and therefore the tin plating layer 33 does not melt at this stage. This first heating treatment is a preliminary step for quickly melting the tin plating layer 33 in the second heating treatment.

[0066] In this first heating process, if the temperature in the first furnace is less than 150°C or the heating time is less than 3 seconds, heating is insufficient, resulting in insufficient formation of the copper-tin alloy in the second heating process, making it difficult to form a copper-tin alloy layer 24 with the desired average thickness. Furthermore, the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer described above is small, and the circularity is low, making it difficult to reliably control within the specified range. On the other hand, if the temperature in the first furnace exceeds 270°C or the temperature of the plated layer-attached substrate 35 exceeds the melting point of tin, causing the tin plating layer 33 to melt during the first heating process, the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24 increases, resulting in reduced wear resistance. Furthermore, the tin layer 25 becomes thinner, resulting in increased contact resistance. If the heating time exceeds 30 seconds, excessive heating occurs, resulting in a thinner tin layer 25 and increased contact resistance.

[0067] Furthermore, in the second heating treatment, if the second furnace temperature is below 232°C or the time is less than 3 seconds, the copper-tin alloy is not sufficiently formed, making it difficult to form a copper-tin alloy layer 24 of the desired average thickness. This results in a small Spc, which increases the friction coefficient and reduces wear resistance. On the other hand, if the second furnace temperature exceeds 350°C, overheating occurs, increasing the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24, thereby increasing the friction coefficient and reducing wear resistance. Furthermore, the tin layer 25 becomes thinner, resulting in increased contact resistance. Similarly, if both the first furnace temperature and the second furnace temperature exceed a predetermined temperature, overheating occurs, increasing the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24, thereby increasing the friction coefficient and reducing wear resistance. Furthermore, the tin layer 25 becomes thinner, resulting in increased contact resistance. If the second heating treatment time exceeds 35 seconds, the tin layer 25 becomes thinner, resulting in increased contact resistance. However, if the tin plating layer 33 is thick or the copper plating layer 32 is thin, the tin layer 25 will become thick even if the heating temperature is high or the heating time is long.

[0068] This second heat treatment melts the tin plating layer of the plated layer-provided substrate 35. The melting of the tin plating layer can be confirmed because the surface changes from white to a glossy silver color when the tin of the plated layer-provided substrate 35 melts.

[0069] In this second heat treatment, the outermost tin plating layer melts and becomes glossy, and then the cooling treatment is immediately performed. Therefore, in this second heat treatment, the plated layer-attached substrate 35 is always in an elevated temperature state and is not maintained at the peak temperature at which the tin melts.

[0070] In this reflow process, the relationship between the furnace temperature and the time required to pass through the furnace is such that the higher the furnace temperature, the shorter the time. For example, in the first heating process, if the furnace temperature is closer to 150°C, the time is longer (about 30 seconds), and if the furnace temperature is closer to 270°C, the time is shorter (about 3 seconds). The same is true for the second heating process, where if the furnace temperature is closer to 232°C, the time is longer (about 35 seconds), and if the furnace temperature is closer to 350°C, the time is shorter (about 3 seconds).

[0071] In this case, the relationship between the furnace temperature and the time may be subdivided within a predetermined temperature range. For example, in the first heating treatment, the time is more than 19 seconds but not more than 30 seconds when the furnace temperature is 150°C or higher but less than 200°C, more than 8 seconds but not more than 19 seconds when the furnace temperature is 200°C or higher but less than 250°C, and 3 seconds or more but not more than 8 seconds when the furnace temperature is 250°C or higher but less than 270°C. In the second heating treatment, the time is more than 23 seconds but not more than 35 seconds when the furnace temperature is 232°C or higher but less than 280°C, more than 11 seconds but not more than 23 seconds when the furnace temperature is 280°C or higher but less than 320°C, and 3 seconds or more but not more than 11 seconds when the furnace temperature is 320°C or higher but less than 350°C. This subdivision may be set taking into consideration ease of management, etc. The first and second heating furnaces are arranged side by side with no gap between them, and the plated layer-formed substrate 35 passes continuously from the first heating furnace to the second heating furnace.

[0072] Furthermore, in the cooling treatment, the cooling time until the temperature of the plated layer-provided substrate 35 reaches 50° C. is preferably set to 4 seconds or more and 60 seconds or less. Under atmospheric cooling conditions, it is physically difficult to cool the plated layer-provided substrate 35 until the temperature reaches 50° C. in a cooling time of less than 4 seconds. However, if the temperature of the plated layer-provided substrate 35 is cooled to 50° C. for a cooling time of more than 60 seconds, the formation of a copper-tin alloy is not sufficiently suppressed, and the alloy shape may no longer be circular, resulting in a low circularity.

[0073] This cooling treatment is initiated immediately after the tin plating layer of the plated layer-formed substrate 35 is melted in the second heating treatment, for example, within 2 seconds, preferably within 1 second after melting. Strictly speaking, cooling of the plated layer-formed substrate 35 begins near the exit of the second heating furnace. Cooling can be performed by spraying cold air or water on the plated layer-formed substrate 35 after it has exited the second heating furnace, passing the plated layer-formed substrate 35 through a water tank, or the like.

[0074] By performing the reflow treatment in this manner, a state is achieved in which a nickel layer 23, a copper-tin alloy layer 24, and a tin layer 25 are formed in this order as a coating 22 on the substrate 21. As described above, since the plating layers 31 to 33 are formed not only on the front and back surfaces of the substrate 21 but also on both side surfaces, a coating 22 consisting of the nickel layer 23, the copper-tin alloy layer 24, and the tin layer 25 is formed on both side surfaces as well as on the front and back surfaces, and the entire surface of the substrate 21 is covered with the coating 22.

[0075] During the reflow treatment, the copper in the copper plating layer 32 and the tin in the tin plating layer 33 react to form the copper-tin alloy layer 24 and the tin layer 25, but some of the copper in the copper plating layer 32 may remain unreacted, and a thin copper layer may exist between the nickel layer 23 and the copper-tin alloy layer 24.

[0076] In the case of a pin-shaped terminal using the terminal material 1 of this embodiment, as shown in Fig. 1, the connecting portion 13 to be connected to the mating terminal is formed in a long, thin pin shape, so that not only the front and back surfaces but also the side surfaces of the terminal material 1 may come into contact with the mating terminal. In addition, since the coating 22 is formed on the entire surface, corrosion is less likely to occur.

[0077] Furthermore, as a result of the inventors' intensive research, it was discovered that by optimizing the shapes of both copper-tin alloy layers in the combination of terminals, this developed product can achieve even lower friction when the terminals slide.

[0078] That is, in a pair of terminals that are fitted together, the difference in the arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer 24 is set to 200 mm. －１ Over 1200mm －１ An even lower friction can be obtained by setting the difference in circularity of the copper-tin alloy particles on the surface of the copper-tin alloy layer 24 to the range of 0.4 or less.

[0079] The difference between the SPC of the female terminal material and the SPC of the male terminal material is 200 mm －１ Over 1200mm －１ In the following cases, the unevenness of the copper-tin alloy layer 24 is appropriately different, so that when sliding, the copper-tin alloy layer 24 has multiple contact points, the pressure at each contact point is small, and the force is dispersed, resulting in a lower coefficient of friction and a reduced amount of wear.

[0080] In the case of such a combination of terminals, the above-described coating 22 may be formed on at least one of the terminals, and the other terminal may have a surface of the copper-tin alloy layer 24 whose arithmetic mean curvature Spc or circularity is within the ranges described in the embodiment (Spc is 700 mm or less). －１ Over 2200mm －１ Hereinafter, the circularity may be outside the range of 0.5 or more.

[0081] In addition, the detailed configuration is not limited to that of the embodiment, and various modifications can be made within the scope that does not deviate from the spirit of the present invention.

[0082] In the connector terminal material 1 of the embodiment, the coating 22 is formed on the entire surface of the substrate 21, but it is sufficient that it is formed at least on the connecting portion 13. Even in this connecting portion 13, the coating 22 does not necessarily have to be formed on the entire surface of both the front and back surfaces and both sides, but it is sufficient that the coating 22 is formed on the portion that comes into contact with the mating member. Furthermore, the substrate fixing portion 15 does not necessarily have to have this coating 22, but may have a tin surface layer made of tin or a tin alloy formed on the entire surface (front, back, and both sides). When the coating 22 is formed on the substrate fixing portion 15, the tin surface layer becomes the tin layer 25.

[0083] The substrate was a 0.40 mm thick CDA (Copper Development Association) alloy designated C18665. After punching out the chain-terminal shape shown in the figure, the substrate was pretreated with electrolytic degreasing and pickling, and then nickel-plated, copper-plated, and tin-plated in that order. Pickling was also performed between the nickel and copper plating. The conditions for electrolytic degreasing, pickling, and plating are shown in Table 1, in order of process, and were the same for the following examples and comparative examples. In the table, RT stands for room temperature.

[0084]

[0085] The substrates with plated layers formed in this manner with various thicknesses were subjected to a reflow treatment. The thickness of each plated layer, the reflow conditions, etc. are shown in Table 2. The cooling time is the time required for the temperature of the substrate with plated layers to reach 50°C.

[0086] When measuring the thickness of each plating layer before and after the reflow treatment, the measurement was performed at part A in Fig. 1. Part A is the central part of the connection part 13 of the terminal.

[0087] The thicknesses of the copper layer and the copper-tin alloy layer in part A, where the three plating layers were formed, were measured by cutting the sample, embedding the cut surface in resin so that it could be observed, and then polishing and CP (cross-section polisher) processing were performed. A cross-sectional backscattered electron image was observed using a scanning electron microscope Reguls 8230 manufactured by Hitachi High-Tech Corporation, and the thicknesses were measured at 10 arbitrary points and the average was calculated. The thicknesses of the tin layer and the nickel layer in part A were also measured using a fluorescent X-ray film thickness meter (FT150) manufactured by Hitachi High-Tech Science Corporation.

[0088]

[0089] For the terminal material after reflow treatment, 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 circularity 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, and the wear resistance (wear amount), friction coefficient, and contact resistance were evaluated.

[0090] (Average Thickness of Each Layer) When measuring the average thickness of each layer, the measurement portion was part A in Fig. 1. Part A is the central portion of the connection portion of the terminal.

[0091] The thickness of the tin layer and the nickel layer was measured using a fluorescent X-ray film thickness meter (FT150) manufactured by Hitachi High-Tech Science Corporation.

[0092] Regarding the average thickness of the tin layer before and after the reflow treatment, first, the thickness of the tin-containing layer (layer containing tin: the entire tin layer and copper-tin alloy layer) of the sample after the reflow treatment was measured, and then the tin layer was removed by immersing the sample for several minutes in an etching solution for stripping tin plating films, such as L80 manufactured by Leybold Co., Ltd., which contains components that etch tin but do not corrode copper-tin alloys, and the average thickness of the tin layer was defined by subtracting the thickness of the tin-containing layer after etching from the thickness of the tin-containing layer before etching.

[0093] The average thickness of the copper-tin alloy layer was determined by cutting a sample, embedding the cut surface in resin so that it would serve as the observation area, polishing and CP (cross-section polisher) processing, and observing a cross-sectional backscattered electron image using a scanning electron microscope Reguls 8230 manufactured by Hitachi High-Technologies Corporation. The thickness was measured at 10 arbitrary locations along the distance a between the peaks of the nickel layer and the copper-tin alloy layer and the distance b between the nickel layer and the copper-tin alloy layer in Figure 2, which shows a schematic cross-section, and the height of the copper-tin alloy layer was calculated as (a + b) / 2, and the average was determined.

[0094] (Arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer) The arithmetic mean curvature Spc of the peaks of the protrusions in part A in Figure 1 was measured by immersing the sample in an etching solution for stripping tin plating films to remove the tin layer and exposing the copper-tin alloy layer underneath, and then using a laser microscope (VK-X200) manufactured by Keyence Corporation with an objective lens magnification of 150 (measurement field of view 96 μm × 72 μm) to measure Spc over a 20 μm square area, and the obtained data was filtered with the cutoff wavelength of the S filter set to 1 μm and the cutoff wavelength of the L filter set to 0.1 mm. The average value of Spc measured at a total of five points was obtained.

[0095] (Circularity of copper-tin alloy particles on the surface of copper-tin alloy layer) The tin layer was removed by immersion in an etching solution for stripping tin plating films, and the copper-tin alloy layer underneath was exposed. The measurement area was designated as area A, and the circularity of the copper-tin alloy particles was measured at 0.0008 mm at a magnification of 4000 times using a SEM (Scanning Electron Microscope) (JCM-7000 manufactured by JEOL Ltd.). ２ The secondary electron image of the field of view was observed. The circularity, which indicates the degree of circularity, was calculated by 4π × (alloy area) ÷ (perimeter) ２ The circularity of at least 10 or more copper-tin alloy particles was obtained per secondary electron image and averaged to determine the circularity.

[0096] (Exposed Area Ratio of Copper-Tin Alloy Layer on the Surface of Tin Layer) The measurement area was designated as part A, and a scanning electron microscope (SEM) (JSM-7001F manufactured by JEOL Ltd.) was used to measure the exposed area ratio of 0.0028 mm at a magnification of 2000 times. 2 A backscattered electron image of the field of view was observed. The backscattered electron image obtained above was binarized using the well-known image processing software Image J (ver. 1.54f) so that the Cu-Sn alloy layer exposed on the surface appeared black and the Sn layer appeared white, and the exposed area ratio was calculated by determining the area of ​​the Cu-Sn alloy layer. The binarization was performed with an altitude range of 255 set to 112.

[0097] (Wear Amount) Each sample was cut into a 60 mm long test piece parallel to the rolling direction and used as a substitute for a male terminal (male terminal test piece). The female terminal test piece was a common specimen. Sample 31 in Table 3, which had not been machined into a terminal shape, was cut into a 60 mm x 10 mm piece and embossed with a 2.5 mm radius of curvature at the center of the test piece. The test was performed using a friction and wear tester (UMT-Tribolab) manufactured by Bruker AXS Co., Ltd. The convex surface of the female terminal test piece was contacted with the sliding portion of the horizontally placed male terminal test piece, part A in Figure 1, and the male terminal test piece was slid back and forth over a distance of 1 mm 500 times while applying a load of 1 N to the male terminal test piece. For the measurement, a white light interference microscope (NexView 8300 manufactured by Ametec Co., Ltd.) was used to observe the sliding marks on the male terminal test piece in the depth direction at 20x magnification, perpendicular to the sliding direction. The amount of wear is calculated by taking the cross-sectional wear area of ​​the deepest wear position and measuring it to 300 μm ２ A: Less than 300 μm ２ 1200 μm or more ２ The following are B, 1200 μm ２ Those exceeding this were rated C.

[0098] (Coefficient of Friction) Each sample was cut into a 60 mm long test piece parallel to the rolling direction and used as a substitute for a male terminal (male terminal test piece). The female terminal samples were all the same. Sample 31 in Table 3, unprocessed into a terminal shape, was cut into a 60 mm x 10 mm piece and embossed with a 2.5 mm radius of curvature at the center of the test piece. The coefficient of friction of these test pieces was measured. For the measurement, a friction and wear tester (UMT-Tribolab) manufactured by Bruker AXS Inc. was used. The convex surface of the female terminal test piece was contacted 5 mm below part A in Figure 1, which shows the horizontally placed male terminal test piece, so that this was the center of the sliding area. While applying a load of 5 N to the male terminal test piece, the test piece was slid 10 mm to a position 5 mm above part A. Friction coefficient data was obtained every 0.013 mm of sliding distance, and the average of the friction coefficients obtained at distances of 0.1 mm to 10 mm was used as the friction coefficient value.

[0099] (Contact Resistance) Test specimens were prepared in the same manner as for the coefficient of friction, except that the embossing radius was 1.5 mm. After heating these specimens at 150°C for 250 hours, the contact resistance (mΩ) of each specimen was measured. A friction and wear tester (UMT-Tribolab) manufactured by Bruker AXS was used to measure the contact resistance when the convex surface of the female test specimen was brought into contact with the horizontally placed male terminal test specimen and a load of 5 N was applied to the male terminal test specimen, using the four-terminal method.

[0100] For the specimens in which cracks were generated by the indentation process, the coefficient of friction, the amount of wear, and the contact resistance were not evaluated.

[0101] The results of these measurements are shown in Table 3.

[0102]

[0103] All of Samples 1 to 30 had low coefficients of friction, low wear, and low contact resistance, and were excellent. These samples had nickel layers with average thicknesses of 0.05 μm to 3.00 μm, tin layers with average thicknesses of 0.05 μm to 2.00 μm, and copper-tin alloy layers with average thicknesses of 0.15 μm to 1.55 μm. The arithmetic mean curvature Spc of the peaks on the surface of the copper-tin alloy layer was 700 mm. －１ Over 2200mm－１ It is within the following range:

[0104] Of these, samples 4 and 19 had slightly greater amounts of wear than the others because their circularity was not 0.5 or greater. Sample 19 had an exposed area ratio of the copper-tin alloy layer that exceeded the specified range. This is presumably due to the long cooling time required to lower the temperature of the plated substrate to 50°C in the reflow treatment process. Samples 28 to 30 had a larger average thickness of the tin layer than the others, resulting in a smaller exposed area ratio of the copper-tin alloy layer.

[0105] Figure 5 is a backscattered electron (BSE) image of the cross section of sample 3. It shows that a copper-tin alloy layer with irregularities is formed on the nickel layer, and a tin layer is formed on top of that. The copper-tin alloy layer also shows that the Cu layer is formed on the nickel layer in a slightly dispersed state. ３ Sn layer and its Cu ３ On the Sn layer and Cu ３ A Cu layer formed over a nickel layer where no Sn layer is present. ６ Sn ５ It was confirmed that the layer consisted of

[0106] In contrast to these samples, sample 31 had a tin layer with an average thickness within the specified range, but had a large Spc and a large amount of wear. This is presumably due to the high temperature in the first furnace during the reflow treatment process. Samples 32 and 37 had copper-tin alloy layers that were too thin to measure the Spc and circularity, and also had a high coefficient of friction and a large amount of wear. This is due to the fact that either the first or second heating treatment in the reflow treatment process was not performed.

[0107] Samples 33 and 34 had a thin copper-tin alloy layer and a small Spc, resulting in a high friction coefficient and a large amount of wear. This is presumably due to an insufficient first heat treatment during the reflow treatment process.

[0108] In sample 35, the temperatures in the first furnace and the second furnace during the reflow treatment were too high, resulting in a large Spc and a large amount of wear. In addition, the tin layer was thin, resulting in high contact resistance.

[0109] In sample 36, the first heat treatment time in the reflow treatment step was too long, so the tin layer became thin and the contact resistance was high.

[0110] Samples 38 and 39 had a high coefficient of friction and a large amount of wear due to their small Spc. This is presumably due to an insufficient second heat treatment in the reflow treatment step.

[0111] In sample 40, the temperature in the second furnace during the reflow treatment was too high, resulting in a large Spc and reduced wear resistance. On the other hand, the tin layer was thin, resulting in high contact resistance.

[0112] In sample 41, the second heat treatment time in the reflow treatment step was too long, so the tin layer became thin and the contact resistance was high.

[0113] In Sample 42, the tin plating layer was too thick, resulting in a high coefficient of friction. In Samples 43 and 44, the copper plating layer remained even after the reflow treatment step.

[0114] In sample 43, the copper plating layer met the specified thickness, but the tin plating layer did not. Therefore, the exposure rate after reflow treatment was greater than specified, resulting in a smaller SPC and a larger amount of wear. Furthermore, the thin tin layer resulted in high contact resistance. Conversely, in sample 44, the copper plating layer was thicker than the specified range, resulting in the average thickness of the copper-tin alloy layer after reflow treatment being greater than the specified range and the tin layer being thinner, resulting in a larger exposure rate than specified. Furthermore, residual copper plating was observed after reflow treatment, and the shape of the copper-tin alloy layer became smoother, resulting in a slightly smaller SPC and within the specified range. Therefore, the amount of wear was somewhat greater. Furthermore, the thin tin layer resulted in high contact resistance.

[0115] In sample 45, the thickness of the copper plating layer and the average thickness of the copper-tin alloy layer were thinner than the specified range, so part of the copper-tin alloy was replaced with nickel, the shape of the copper-tin alloy became steep, and Spc was larger than the specified range, resulting in a high friction coefficient and a large amount of wear.

[0116] The nickel layer of sample 46 was too thick, causing cracks during indentation, and therefore the friction coefficient, wear amount, and contact resistance were not evaluated.The nickel layer of sample 47 was too thin, resulting in high contact resistance.

[0117] In sample 48, the temperatures of the first and second heat treatments during the reflow treatment were the same, so the copper-tin alloy layer did not assume the desired shape, the Spc was smaller than the desired range, and the amount of wear was large.

[0118] In sample 49, the temperature of the second heat treatment during the reflow treatment was lower than the temperature of the first heat treatment, so the copper-tin alloy layer did not take on the desired shape, the Spc was smaller than the desired range, and the amount of wear was large.

[0119] Next, the above samples were arbitrarily combined, and the difference in Spc and circularity of the copper-tin alloy layer was determined, and the friction coefficient was measured. In this case, one was used as a male terminal and the other as a female terminal, and the friction coefficient was measured in the same manner as above. The results are shown in Table 4.

[0120]

[0121] All combinations have a good coefficient of friction, but the difference in Spc between the female terminal and the male terminal is 200 mm. -１ Over 1200mm －１ The following samples 53 to 62 show particularly good friction coefficients. The difference in circularity in all cases was 0.4 or less. It is assumed that the appropriate difference in the shape of the copper-tin alloy layer reduces the contact points of the copper-tin alloy layer during sliding, and the actual contact area is reduced, resulting in smaller sliding marks. Note that sample 52 is within the scope of the present invention for both the male and female terminals, but the difference in Spc is 200 mm. -１ The friction coefficient was slightly higher because the

[0122] The Spc of one side terminal of samples 55, 56, 59, and 60 is 2200 mm －１ However, the Spc of the other terminal is appropriate, resulting in a low coefficient of friction.

[0123] On the other hand, for sample 51, the Spc for both the female terminal and the male terminal was 2200 mm. －１The difference in SPC between the female terminal and the male terminal was 1200 mm. －１ Samples 63 and 64, which exceeded 100%, showed slightly higher values ​​of the friction coefficient. This is presumably because the uneven shape of the copper-tin alloy layer of one terminal is thinner than the uneven shape of the copper-tin alloy layer of the other terminal, which may cause breakage during sliding.

[0124] INDUSTRIAL APPLICABILITY The present invention can be used for an in-vehicle connector used for connecting electrical wiring in an automobile or the like.

[0125] REFERENCE SIGNS LIST 1 Connector terminal material 10 Terminal portion 11, 12 Linking member 13 Connection portion 14 Shoulder portion 15 Substrate fixing portion 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 Base material with plating layer

Claims

1. A film is formed on the surface of a base material made of copper or a copper alloy, and the film has a nickel layer made of nickel or a nickel alloy formed on the surface of the base material, a copper-tin alloy layer made of an alloy of copper and tin formed on the nickel layer, and a tin layer made of tin or a tin alloy formed on the copper-tin alloy layer. The average thickness of the nickel layer is 0.05 μm or more and 3.00 μm or less. The arithmetic mean curvature Spc of the peak points on the surface of the copper-tin alloy layer is 700 mm －１ or more and 2200 mm －１ or less, 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. A terminal material for a connector characterized by the above.

2. Remove the tin layer of the film to expose the copper-tin alloy layer, and the circularity of the copper-tin alloy particles on the surface of the exposed copper-tin alloy layer is 0.5 or more. The terminal material for a connector according to claim 1.

3. A part of the copper-tin alloy layer is exposed on the surface of the tin layer, and the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer is 5% or more and 70% or less. The terminal material for a connector according to claim 1 or 2.

4. It has a connection part connected to the counterpart side and a board fixing part fixed to the board, and at least the connection part is formed with the film. The terminal material for a connector according to claim 1 or 2.

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

6. It has one-side terminals and the other-side terminals that can be connected to each other, and at least one of these one-side terminals and the other-side terminals is made of the connector terminal material described in claim 1 or 2, and the difference in the arithmetic mean curvature Spc of the peak points on the surface of the copper-tin alloy layer between the one-side terminal and the other-side terminal is 200 mm －１ or more and 1200 mm －１ or less. A connector characterized by this.

7. The difference in the circularity of the copper-tin alloy particles on the surface of the copper-tin alloy layer between the one-side terminal and the other-side terminal is in the range of 0.4 or less. The connector according to claim 6.

8. A plating layer forming step of forming 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 performing a reflow treatment of heating the base material with a plating layer. In the plating layer forming step, the thickness of the nickel plating layer is 0.05 μm or more and 3.00 μm or less, the thickness of the copper plating layer is 0.10 μm or more and 0.70 μm or less, and the thickness of the tin plating layer is 0.20 μm or more and 2.90 μm or less. The reflow treatment step includes a first heat treatment of passing the base material with a plating layer through a first heating furnace set at a first furnace internal temperature of 150°C or more and 270°C or less in an air atmosphere within a time of 3 seconds or more and 30 seconds or less to heat the base material with a plating layer to below the melting point of tin, a second heat treatment of passing the base material with a plating layer through a second heating furnace set at a second furnace internal temperature higher than the first furnace internal temperature, which is 232°C or more and 350°C or less, within a time of 3 seconds or more and 35 seconds or less to heat it, and a cooling treatment of rapidly cooling the base material with a plating layer immediately after the tin plating layer is melted by the second heat treatment. A method for manufacturing a terminal material for a connector, characterized by having the above steps.

9. The method for manufacturing a terminal material for a connector according to claim 8, wherein in the cooling treatment, the cooling time until the temperature of the substrate with the plating layer reaches 50°C is 4 seconds or more and 60 seconds or less.

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