Terminal material for connector and method for manufacturing same

Abstract

In the present invention, the average thickness of a nickel layer is 0.15-4.0 mm, and the average thickness of a copper-tin alloy layer is 0.15-0.8 μm. In a cross section parallel to a rolling direction of a base material, when the area ratio of a tin layer to the total area of the copper-tin alloy layer and the tin layer of a connection part is taken as X% and the area ratio of the tin layer to the total area of the copper-tin alloy layer and the tin layer of a soldering part is taken as Y%, X % is 21%-50%, Y % is 31%-90%, Y > X, and a difference therebetween is 10% or more.

Description

Connector terminal material and method for manufacturing the same

[0001] The present invention relates to a connector terminal material that reduces the insertion force during connector mating and improves solder wettability during mounting, and a method for manufacturing the same.

[0002] This application claims priority based on Japanese Patent Application No. 2024-186655, filed in Japan on October 23, 2024, and the contents of that application are incorporated herein by reference.

[0003] Conventionally, connectors used for connecting electrical wiring in automobiles, consumer electronics, etc., have terminal pairs designed so that an electrical connection is made when a contact piece provided on a female terminal and a male terminal inserted into the female terminal come into contact with each other at a predetermined contact pressure.

[0004] As such connectors (terminals), terminal materials are known in which a copper-tin alloy layer and a tin layer are formed on a base material made of copper or a copper alloy by applying copper plating and tin plating to the base material and then performing a reflow process.

[0005] In terminal materials with such copper-tin alloy layers and tin layers, for example, Patent Document 1 reduces insertion force by controlling the roughness of the base material and controlling the degree to which the copper-tin alloy layer is exposed from the tin layer. However, it is necessary to process the base material in advance to control its roughness. For this reason, it is difficult to apply this to terminal materials that are manufactured by punching out small terminals with complex shapes and then plating them.

[0006] Furthermore, while Patent Document 2 reduces insertion force by making the tin layer, which is made of tin or a tin alloy, on the copper-tin alloy layer very thin, there is a problem that the contact resistance increases in high-temperature and high-humidity environments due to the small amount of tin layer.

[0007] Furthermore, in Patent Document 3, a portion of the copper-tin alloy is replaced with nickel (Ni), creating a steep, uneven shape in the copper-tin alloy while leaving a certain amount of the tin layer to reduce friction and prevent an increase in contact resistance in high-temperature environments. However, because the copper-tin alloy layer is steep, there are limits to how much the insertion force can be reduced.

[0008] However, when these terminal materials are formed into terminals, fracture surfaces are created, which leads to a problem of reduced solder wettability. To prevent this, it is conceivable to perform plating and reflow treatment after forming the terminal shape. However, in all terminal materials, the tin layer needs to be thin to maintain low friction, so if there is a long time between the plating treatment and the reflow treatment, or if the material is exposed to a high temperature and high humidity environment, there is a problem of reduced solder wettability.

[0009] Japanese Patent Publication No. 2007-100220, Japanese Patent Publication No. 2011-012320, Japanese Patent Publication No. 2014-240520

[0010] In these terminal materials, the soft tin layer on the surface is prone to adhesion during insertion and removal, resulting in high insertion force. Therefore, attempts are made to reduce the insertion force by thinning the tin layer and exposing part of the copper-tin alloy layer. However, this leads to insufficient solder wettability during mounting. To ensure sufficient solder wettability, the tin layer must be thickened, which increases the insertion force. Thus, achieving both reduced insertion force and improved solder wettability has been difficult.

[0011] Furthermore, during reflow processing, when nickel from the nickel layer diffuses into the copper-tin alloy layer, pores form in the nickel layer, reducing its barrier properties, and over time, an oxide layer forms on the surface of the tin layer.

[0012] This invention has been made in view of these circumstances, and aims to achieve both a reduction in insertion force and an improvement in solder wettability in high-temperature, high-humidity environments, thereby increasing durability against temperature changes.

[0013] The connector terminal material of the present invention has a base material made of rolled copper or copper alloy, on which a coating is formed comprising a nickel layer made of nickel or a nickel alloy formed on the surface of the base material, a copper-tin alloy layer made of a copper-tin alloy formed on the nickel layer, and a tin layer made of tin or a tin alloy formed on the copper-tin alloy layer, and has a connection portion for connection to the mating side and a soldering portion for soldering to a substrate, wherein the average thickness of the nickel layer is 0.15 μm or more and 4.0 μm or less, and the average thickness of the copper-tin alloy layer is 0.15 μm or more and 0.8 μm or less, and in a cross section parallel to the rolling direction of the base material, if the ratio of the cross-sectional area of ​​the tin layer to the total area of ​​the copper-tin alloy layer and the tin layer in the connection portion is X%, and the ratio of the cross-sectional area of ​​the tin layer to the total area of ​​the copper-tin alloy layer and the tin layer in the soldering portion is Y%, then X% is 21% or more and 50%, and Y% is 31% or more and 90%. Y > X, and the difference between them is 10% or more.

[0014] The nickel layer has a barrier function that prevents the diffusion of copper and other components (substrate components) from the substrate at high temperatures, thereby improving heat resistance. The greater the average thickness of this nickel layer, the higher the heat resistance, but beyond a certain thickness it is unnecessary and prone to cracking during processing. On the other hand, if the average thickness of the nickel layer becomes too small, the barrier function against the substrate components is insufficient, reducing solder wettability, increasing contact resistance in high-temperature and high-humidity environments, and worsening durability against temperature changes.

[0015] Furthermore, the copper-tin alloy layer and the tin layer are a composite structure in which the relatively soft tin layer on the surface is supported by the hard copper-tin alloy layer. Because the interface has an uneven shape, the coefficient of friction can be reduced in combination with the lubricating effect of the tin layer.

[0016] If the average thickness of the copper-tin alloy layer exceeds 0.8 μm, the tin layer remaining after reflow soldering becomes thinner, resulting in higher contact resistance in high-temperature and high-humidity environments, reduced durability against temperature changes, and a higher coefficient of friction. On the other hand, if the average thickness of the copper-tin alloy layer is less than 0.15 μm, the tin layer becomes thicker, and the amount of hard copper-tin alloy layer decreases, resulting in a higher coefficient of friction. The same applies to soldered joints, but it is particularly effective in connection areas.

[0017] Regarding the cross-sectional area ratio of the copper-tin alloy layer and the tin layer in a cross-section parallel to the rolling direction, when the cross-sectional area ratio of the tin layer is high and the surface irregularities of the copper-tin alloy layer are small, the exposed area ratio of the copper-tin alloy layer on the tin layer surface decreases. Conversely, when the cross-sectional area ratio of the tin layer is low and the irregularities of the copper-tin alloy layer are large, the exposed area ratio tends to increase. At the connection point, friction is reduced by lowering the cross-sectional area ratio of the tin layer and increasing the surface irregularities of the copper-tin alloy layer, thereby increasing the exposed area ratio of the copper-tin alloy layer. However, if the cross-sectional area ratio of the tin layer is too low and the surface irregularities of the tin-copper alloy layer become too small, the coefficient of friction tends to increase.

[0018] When terminals are formed in a narrow pin shape, plating them to form a coating easily results in differences in coating thickness between the flat and corner portions, and measuring the coating thickness at the corners is difficult. Therefore, relying solely on controlling the average thickness of the coating on the flat portion of the terminal may make it difficult to ensure good solder wettability. To address this, in addition to the average thickness of the copper-tin alloy layer, the ratio of the cross-sectional area of ​​the tin layer to the total area of ​​the copper-tin alloy layer and the tin layer is specified. This ratio of the cross-sectional area of ​​the tin layer is not strictly proportional to the exposed area ratio of the copper-tin alloy layer, but there is a certain degree of correlation.

[0019] At the connection point, if the cross-sectional area ratio of the tin layer exceeds 50%, the tin layers will adhere to each other during sliding, increasing the coefficient of friction. If it is less than 21%, the contact resistance in high-temperature and high-humidity environments will increase, resulting in poor durability against temperature changes.

[0020] In soldering joints, if the cross-sectional area ratio of the tin layer exceeds 90%, the cross-sectional area ratio of the tin layer at the connection point also increases, making it difficult to reduce friction. If it falls below 31%, solder wettability decreases.

[0021] As mentioned above, the cross-sectional area ratio is reduced at the connection point to reduce friction, but if it is too low at the soldering point, the solder wettability will decrease. Therefore, a balance between the two parts is important, and if the difference in the cross-sectional area ratio of the tin layer between the connection point and the soldering point (Y-X) is 10% or more, it is possible to achieve both low friction at the connection point and good solder wettability at the soldering point in high temperature and high humidity environments.

[0022] In the connector terminal material of the present invention, the soldered portion is preferably such that the skewness Ssk of the nickel layer after the tin layer and the copper-tin alloy layer have been removed is 0 or more and 0.6 or less.

[0023] Skewness Ssk is a parameter that extends the contour curve (line roughness) parameter Rsk to three dimensions, and like Rsk, it is a parameter that evaluates the degree of bias (skewness: wideness) of the histogram of the height distribution.

[0024] A skewness Ssk of 0 or greater indicates that the height distribution is symmetrical vertically, suggesting few defects in the nickel layer. A negative skewness Ssk indicates a surface with many fine valleys, suggesting a high number of defects.

[0025] A good nickel layer Ssk value in the solder joint results in lower contact resistance in higher temperature environments and greater durability against temperature changes. Since the Ssk values ​​of the solder joint and the connection are considered to be approximately the same, a nickel layer without defects provides high barrier properties against the substrate components in high-temperature and high-humidity environments. However, materials with a skewness Ssk exceeding 0.6 are difficult to manufacture.

[0026] In the connector terminal material of the present invention, the exposed area ratio of the copper-tin alloy layer exposed from the tin layer on the surface of the coating is preferably 20% or more at the connection portion and less than 10% at the soldering portion.

[0027] For connection points, a higher exposed area ratio of the copper-tin alloy layer is preferable to reduce insertion force; if it is less than 20%, the effect of reducing insertion force is insufficient. Conversely, for soldering points, a lower exposed area ratio of the copper-tin alloy layer is preferable; if it is 10% or more, solder wettability may decrease in high-temperature, high-humidity environments.

[0028] For connector terminals that are fixed to a circuit board by soldering, it is preferable to use a "post-plating method" in which a metal plate is plated after it has been punched out. In the case of pin-shaped terminals, the post-plating method forms coatings on the entire surface of the connection part with the mating side and the soldering part, resulting in a terminal that has excellent insertion / extraction properties with the mating terminal, as well as excellent solder wettability.

[0029] The present invention relates to a method for manufacturing a connector terminal material having a connection portion that is connected to a mating side and a soldering portion that is soldered to a substrate, 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 and a tin alloy are formed in this order on a substrate made of rolled copper or a copper alloy to obtain a substrate with plating layers, and the thickness of the tin plating layer is formed such that the portion to be soldered is thicker than the portion to be connected, and then the portion to be soldered is subjected to an activation treatment with an activation treatment solution containing phosphorus, and then reflow treatment.

[0030] By performing an activation treatment before the reflow process, the soldered portion having a thick tin plating layer can be effectively dissolved during the reflow process, and both the soldered portion and the connection portion can be formed into a uniformly molten surface state.

[0031] In that case, the base material may have a terminal chain formed in advance by pressing, in which multiple terminal members are connected.

[0032] According to the present invention, by forming the thickness of the tin layer and the cross-sectional area ratio of the tin layer between the connection part and the soldered part within a predetermined range, it is possible to achieve both a reduction in insertion force at the connection part and an improvement in solder wettability at the soldered part.

[0033] This is a plan view of a connector terminal material according to an embodiment of the present invention. This is a schematic cross-sectional view of the connector terminal material of Figure 1. This is a flowchart showing the manufacturing method of the connector terminal material of Figure 1. This is a schematic cross-sectional view showing the plated substrate of the connector terminal material of Figure 2 before the reflow process. This is a secondary electron image of the tin layer surface at the soldering area obtained by scanning electron microscopy.

[0034] Embodiments of the present invention will be described below with reference to the drawings.

[0035] [Configuration of Connector Terminal Material] As shown in Figure 1, the connector terminal material 1 of this embodiment is a terminal chain formed by connecting multiple terminal members 10 that have the shape of pin terminals, and is formed by punching out a long sheet of material by press processing.

[0036] Specifically, on one side of a long, narrow connecting member 11 of a predetermined width that is continuous in the left-right direction as shown in Figure 1, a plurality of long, narrow terminal members 10 are provided in parallel at predetermined intervals along a direction perpendicular to the length direction of the connecting member 11. Each terminal member 10 has a pin-shaped connecting portion 13 and a soldering portion 14 that is narrower than the connecting portion 13, which are formed continuously from the tip, and the base end of the soldering portion 14 is connected to the connecting member 11 at a right angle. After being detached from the connecting member 11, the terminal member 10 is used in an electrically connected state to a substrate by soldering the soldering portion 14 to a through-hole or the like on the substrate, and an electrical connection is made by inserting the connecting portion 13 into another female terminal.

[0037] For example, the plate thickness is formed to be 0.06 mm or more and 1.00 mm, and the width of the connecting portion 13 is formed to be 0.1 mm or more and 2.0 mm or less. However, Figure 1 is just one example, including the shape of the terminal member 10, and is not limited to what is shown in Figure 1. Any device that has a connecting portion that makes an electrical connection with a mating terminal is acceptable.

[0038] And this connector terminal material 1 has a connection part film 22 and a soldering part film 23 formed on a base material 21 made of copper or a copper alloy, respectively. These films 22 and 23 have a common layer structure, in which nickel layers 31 and 32 made of nickel or a nickel alloy, copper-tin alloy layers 33 and 34 made of an alloy of copper and tin, and tin layers 35 and 36 made of tin or a tin alloy are formed on the base material 21 in this order. The tin layers 35 and 36 constitute the surface layers of the films 22 and 23.

[0039] Although FIG. 2 shows a cross section in the thickness direction, the films 22 and 23 are formed on the entire front and back surfaces and both side surfaces of the base material 21.

[0040] As long as the base material 21 is made of a rolled material of copper or a copper alloy, its composition is not particularly limited. For example, it is composed of a plate material made of oxygen-free copper (C10200), a Cu-Mg-based copper alloy (C18665), brass, phosphor bronze, or other copper or copper alloys. The left-right direction in FIG. 1 is the rolling direction. Also, the surface roughness Ra of the base material 21 is measured in a direction perpendicular to the rolling direction and is 0.01 μm or more and 0.10 μm or less under the condition of a magnification of 150 times, and a flat plate material is used.

[0041] The nickel layers 31 and 32 have a function of suppressing the diffusion of components such as copper (base material components) from the base material 21 to the copper-tin alloy layers 33 and 34 and the tin layers 35 and 36 formed thereon. The average thickness (film thickness) of the nickel layers 31 and 32 is 0.15 μm or more and 4.0 μm or less for both the connection part film 22 and the soldering part film 23.

[0042] The nickel layers 31 and 32 have a barrier function to prevent the diffusion of components such as copper (substrate components) from the substrate 21 at high temperatures, and can improve heat resistance. The greater the average thickness of the nickel layers 31 and 32, the higher the heat resistance. However, a certain thickness (4.0 μm) is sufficient, and any further increase would make the layers prone to cracking during processing. On the other hand, if the average thickness of the nickel layers 31 and 32 becomes too small, the barrier function against substrate components will be insufficient, resulting in a high contact resistance value under high-temperature and high-humidity environments and poor durability against temperature changes. Also, if the average thickness of the nickel layers 31 and 32 becomes too small, copper-tin alloying becomes easier under high-temperature and high-humidity environments, leading to a decrease in solder wetting performance.

[0043] In addition, for the film 23 for the soldering part, it is preferable that the skewness Ssk of the nickel layer 32 is 0 or more.

[0044] The skewness Ssk is a parameter obtained by three-dimensionally expanding the Rsk of the profile curve (line roughness) parameter, and like Rsk, it is a parameter for evaluating the degree of bias (skewness) of the height distribution histogram.

[0045] During reflow, a part of the nickel in the nickel plating layer diffuses into the copper-tin alloy layer. In this case, since it diffuses along the grain boundaries of the copper-tin alloy, the greater the diffusion amount, the more the nickel plating layer sinks into the shape of the grain boundaries. Such a state is a state where a defect occurs in the barrier property of nickel, resulting in a decrease in heat resistance (the tin layer becomes more likely to be copper-tin alloyed by heating).

[0046] When this skewness Ssk is 0 or more (a positive value), it indicates that the height distribution is symmetric about the vertical axis and there are few defects. When the skewness Ssk is negative, it indicates a surface with many fine valleys and many defects.

[0047] If the Ssk of the nickel layer 32 in the soldering portion 14 is lower than 0, the heat resistance of the nickel layer 32 will decrease, which may reduce the solder wettability in a high-temperature, high-humidity environment. It is preferable if the Ssk is 0 or higher, as this maintains heat resistance and prevents a decrease in solder wettability in a high-temperature, high-humidity environment, but it is difficult to manufacture if the Ssk exceeds 0.6. In addition, in the connection portion 13, it is preferable if the nickel layer 31 is free of defects (Ssk is 0 or higher) because it provides a high barrier to the substrate components in a high-temperature, high-humidity environment.

[0048] Furthermore, the composition of the nickel layers 31 and 32 is not particularly limited, as long as they are made of nickel or a nickel alloy. Since the surface of the substrate 21 is flat and the nickel layers 31 and 32 are formed on it with a uniform thickness, the surfaces of the nickel layers 31 and 32 are also formed to be substantially flat.

[0049] The copper-tin alloy layers 33 and 34 are obtained together with the tin layers 35 and 36 by sequentially forming a copper plating layer and a tin plating layer on the nickel layers 31 and 32 and then performing a reflow treatment. ６ Sn ５ Alloy only, or mostly Cu ６ Sn ５ The alloy and a small amount of Cu placed beneath it ３ It is formed by a composite structure with a tin alloy. In addition, some of the copper in the copper plating layer remains unreacted, and a thin copper layer may exist between the nickel layer 32 and the copper-tin alloy layers 33 and 34.

[0050] As shown in Figure 2, the interfaces between the copper-tin alloy layers 33 and 34 and the nickel layers 31 and 32 are formed as nearly flat surfaces, while the surfaces of these layers, i.e., the interfaces with the tin layers 35 and 36 above them, are formed as uneven surfaces. In these copper-tin alloy layers 33 and 34, if the distance from the interface with the nickel layers 31 and 32 to the peaks of the copper-tin alloy layers 33 and 34 is denoted as a, and the distance from the interface with the nickel layers 31 and 32 to the valleys of the copper-tin alloy layers 33 and 34 is denoted as b, then a is formed to be between 0.23 mm and 1.28 mm, and b is formed to be between 0.06 mm and 0.32 mm.

[0051] Furthermore, this hard copper-tin alloy layer 33, 34 forms a composite structure in which the relatively soft tin layer 35, 36 on the surface is supported from below. Combined with the lubricating effect of the tin layer 35, 36, this reduces the coefficient of friction.

[0052] Furthermore, the distance a to the peak of the copper-tin alloy layers 33 and 34 and the distance b to the valley of the copper-tin alloy layers 33 and 34 are in the relationship a > b, and the difference a - b is not necessarily limited, but is formed to be between 0.06 and 1.00.

[0053] Furthermore, in the coating 22 for the connection part, a portion of the copper-tin alloy layer 33 is exposed on the surface of the tin layer 35. In the coating 23 for the soldering part, a portion of the copper-tin alloy layer 33 may be exposed on the surface of the tin layer 35 to a small extent, but it may not be exposed at all.

[0054] The average thickness of the copper-tin alloy layers 35 and 36 is 0.15 μm or more and 0.8 μm or less for both the coating 22 for the connection part and the coating 23 for the soldering part.

[0055] The average thickness of these copper-tin alloy layers 35 and 36 is affected by the reflow treatment conditions described later, as well as the thickness of the tin-plated layers 43 and 44 and the copper-plated layer 42 during manufacturing.

[0056] If the average thickness of the copper-tin alloy layers 33 and 34 is less than 0.15 μm due to insufficient heating during the reflow process, the tin layers 35 and 36 become thicker, and the amount of hard copper-tin alloy layers 33 and 34 decreases, resulting in a higher coefficient of friction. If the average thickness of the copper-tin alloy layers 33 and 34 exceeds 0.8 μm due to excessive formation of copper-tin alloy layers 33 and 34 during the reflow process, the tin layers 35 and 36 become thinner, increasing the contact resistance value in high-temperature and high-humidity environments, resulting in poor durability against temperature changes and a higher coefficient of friction. The same applies to the soldered portion 14, but it is mainly effective in the connection portion 13.

[0057] The average thickness of these copper-tin alloy layers 33 and 34 is preferably 0.30 μm or more and 0.65 μm or less.

[0058] Furthermore, in a cross-section parallel to the rolling direction and along the thickness direction of the base material 21, the cross-sectional area ratio of the tin layers 35 and 36 is 21% to 50% of the total area of ​​the copper-tin alloy layers 33 and 34 and the tin layers 35 and 36 for the connection part coating 22, and 31% to 90% for the soldering part coating 23.

[0059] Regarding the exposed area ratio of the copper-tin alloy layers 33 and 34 and the cross-sectional area ratio of the tin layers 35 and 36, when the cross-sectional area ratio of the tin layers 35 and 36 increases, the exposed area ratio of the copper-tin alloy layers 33 and 34 on the surface of the tin layers 35 and 36 decreases, and when the cross-sectional area ratio of the tin layers 35 and 36 decreases, the exposed area ratio of the copper-tin alloy layers 33 and 34 increases.

[0060] The connection portion 13 aims to reduce friction by lowering the cross-sectional area ratio of the tin layer 35 and increasing the exposed area ratio of the copper-tin alloy layer 33. However, if the cross-sectional area ratio of the tin layer 35 is too low, the coefficient of friction will increase.

[0061] In this connection 13, if the cross-sectional area ratio of the tin layer 35 exceeds 50%, adhesion becomes more likely, making it difficult to reduce friction. If it is less than 21%, the coefficient of friction becomes high, resulting in high contact resistance in high-temperature and high-humidity environments and poor durability against temperature changes.

[0062] In the soldering portion 14, if the cross-sectional area ratio of the tin layer 36 exceeds 90%, the cross-sectional area ratio of the tin layer 35 in the connection portion 13 also increases, making it difficult to reduce friction, and if it is less than 31%, the solder wettability decreases.

[0063] The cross-sectional area ratio of the tin layers 35 and 36 is preferably 25% to 45% at the connection portion 13, and preferably 45% to 75% at the soldered portion 14.

[0064] As mentioned above, the cross-sectional area ratio is reduced in the connection portion 13 to reduce friction, but if it is too small in the soldering portion 14, the solder wettability will decrease. For this reason, a balance between the two portions 13 and 14 is important, and if the difference in the cross-sectional area ratio (Y-X) of the tin layers 35 and 36 between the connection portion 13 and the soldering portion 14 is 10% or more, then friction can be reduced in the connection portion 13 while ensuring good solder wettability in the soldering portion 14 even in high temperature and high humidity environments, thus achieving a good balance between the two.

[0065] Furthermore, on the surfaces of the coatings 22 and 23, the exposed area ratio of the copper-tin alloy layers 33 and 34 exposed from the tin layers 35 and 36 should be 20% or more for the coating 22 for the connection part and less than 10% for the coating 23 for the soldering part.

[0066] For the connection portion 13, a higher exposed area ratio of the copper-tin alloy layer 33 is preferable to reduce insertion force; if it is less than 20%, the effect of reducing insertion force is poor. Conversely, for the soldering portion 14, a lower exposed area ratio of the copper-tin alloy layer 34 is preferable; if it is 10% or more, solder wettability may decrease in high-temperature, high-humidity environments.

[0067] [Method for manufacturing connector terminal material] Next, the method for manufacturing this connector terminal material 1 will be described.

[0068] The manufacturing method for the connector terminal material 1 includes a punching step of punching out an elongated metal plate made of rolled copper or copper alloy by press to form a terminal chain that will become a base material 21; a pre-plating treatment step of cleaning the surface of the base material 21 after punching; a plating layer formation step of sequentially forming a nickel plating layer 41, a copper plating layer 42, and tin plating layers 43, 44 on the surface of the base material 21 after the pre-plating treatment step; a pre-treatment step for reflow processing of the plated base material 45 with the three plating layers (pre-reflow treatment step); and a reflow treatment step of heating the plated base material 45 after the pre-reflow treatment and performing reflow processing (see Figure 3). The process will be described below in order.

[0069] (Punching process) While feeding out an elongated metal plate made of copper or a copper alloy wound in a coil shape, it is punched by a press to form a terminal chain body serving as a base material 21 as shown in FIG. 1.

[0070] (Pretreatment process before plating) The base material 21 after punching is subjected to pretreatment such as degreasing and pickling to clean the surface.

[0071] (Plating layer formation process) On the base material 21 after the pretreatment for plating, a nickel plating layer 41 made of nickel or a nickel alloy, a copper plating layer 42 made of copper or a copper alloy, and tin plating layers 43 and 44 made of tin or a tin alloy are formed in this order as follows (see FIG. 4).

[0072] - Nickel plating layer - A nickel plating treatment for forming a nickel plating layer 41 made of nickel or a nickel alloy is performed on the surface of the pretreated base material 21. A general nickel plating bath may be used for the plating bath. For example, a sulfamic acid bath mainly composed of nickel sulfamate and boric acid can be used. The temperature of the plating bath is 50°C or higher and 60°C or lower, and the current density is 1 A / dm ２ or higher and 10 A / dm ２ or lower. The thickness of this nickel plating layer 41 is 0.15 μm or more and 4.0 μm or less.

[0073] - Copper plating layer - A copper plating treatment for forming a copper plating layer 42 made of copper or a copper alloy is performed on the nickel plating layer 41. General copper plating baths may be used for copper plating. For example, a copper sulfate bath mainly composed of copper sulfate and sulfuric acid can be used. The temperature of the plating bath is 20°C or higher and 50°C or lower, and the current density is 1 A / dm ２ or higher and 10 A / dm ２ or lower. The thickness of this copper plating layer 42 is 0.1 μm or more and 0.5 μm or less.

[0074] -Tin Plating Layer- A tin plating treatment is performed on the copper plating layer 42 to form tin plating layers 43 and 44 made of tin or a tin alloy. A general tin plating bath can be used as the plating bath for forming the tin plating layers 43 and 44. For example, a methanesulfonic acid bath mainly composed of methanesulfonic acid and tin methanesulfonate can be used. The temperature of the plating bath is 20°C to 40°C, and the current density is 1 A / dm ２ 20A / dm or more ２ The following is considered to be the case.

[0075] This tin plating process is controlled so that the tin plating layers 43 and 44 have different thicknesses at the connection point 13 and the soldered point 14.

[0076] Specifically, a plated substrate having a nickel plating layer 41 and a copper plating layer 42 is immersed in a tin plating bath (electroplating bath), and a shielding plate is placed between the area that will become the connection part 13 and the electrode while the plating process (electroplating process) is performed. The shielding plate is an insulating plate made of a material that does not corrode in the plating solution, such as a non-conductive resin (for example, polyvinyl chloride or acrylic resin). By appropriately setting the distance between the shielding plate, the plated substrate, and the electrode, as well as the area of ​​the shielding plate, the thickness of the tin plating layers 43 and 44 at the connection part 13 and the soldering part 14 can be controlled.

[0077] The tin plating layer 43 of the connection portion 13 is controlled to be between 0.3 μm and 2.5 μm in thickness, and the tin plating layer 44 of the soldering portion 14 is controlled to be between 1.0 μm and 4.0 μm in thickness. In this case, the tin plating layer 44 of the soldering portion 14 is formed to be thicker than the tin plating layer 43 of the connection portion 13.

[0078] Alternatively, the thickness may be controlled by performing tin plating multiple times, with at least one of these processes involving masking the surface of the connecting portion before plating.

[0079] In this way, a nickel plating layer 41, a copper plating layer 42, and tin plating layers 43 and 44 are sequentially formed on the surface of the substrate 21, thereby obtaining a plated substrate 45 with three stacked plating layers. Between each plating process, a cleaning treatment using sulfuric acid or the like is performed.

[0080] Before this plating process, the substrate 21 is in a state where it has been punched out into a chain terminal body by a press. The substrate 21 is then immersed in a plating bath to form a plating layer, so three plating layers are formed not only on both the front and back surfaces of the substrate 21, but also on both sides (the cut ends at the time of punching). However, the present invention can also be used in a "partial plating" process in which only a portion of the substrate is immersed in the plating bath.

[0081] (Pre-reflow treatment process) After forming the tin plating layers 43 and 44, the surface is cleaned with water or hot water, and then the side of the tin plating layers 43 and 44 that will become the soldering portion 14 is treated with a pre-reflow activation process. This is to ensure that the tin dissolves uniformly in the soldering portion 14 and the connection portion 13, where the thickness of the tin plating layers 43 and 44 differs.

[0082] As the thickness of the plating layer increases, the surface roughness of the plating layer also increases. When the surface roughness increases, especially when the tin plating layer is the outermost layer, the amount of tin oxide film per unit area increases, making it more difficult for tin to dissolve during reflow soldering. Also, simply put, a thicker tin plating layer requires more heat to dissolve.

[0083] Although the reflow process is performed under the same conditions for both the connection part 13 and the soldering part 14, the thickness of the tin plating layer 44 on the soldering part 14 side and the tin plating layer 43 on the connection part 13 side are different. Therefore, if the reflow conditions are adjusted to melt the thicker tin plating layer 44 of the soldering part 14, the tin plating layer 43 on the connection part 13 side will be over-reflowed. On the other hand, if the reflow conditions are adjusted to melt the thinner tin plating layer 43 on the connection part 13 side, the tin plating layer 44 of the soldering part 14 will be under-reflowed, which may result in unmelted tin crystals.

[0084] Therefore, by performing activation treatment only on the soldering portion 14, which has a thicker tin plating layer, the tin becomes easier to dissolve. As a result, even when heat treatment is performed at the same furnace temperature, the tin can be uniformly dissolved in both the soldering portion 14 and the connection portion 13, resulting in a glossy surface appearance, and the connection portion is not excessively reflowed, keeping the exposed area ratio within an appropriate range.

[0085] If the tin is not completely dissolved, irregularities remain on the surface of the tin layer, increasing the specific surface area. Moisture and other substances tend to remain in the depressions, and under high temperature and high humidity conditions, a large oxide film is more likely to form, worsening solder wetting. In addition, if the tin is not completely dissolved, the electrodeposition stress within the tin plating layer is not released, making it easier for whiskers to form.

[0086] This activation treatment is performed by immersing the tin plating layer 44 of the plated substrate 45, specifically the portion that will become the soldering portion 14, in a surface treatment solution before the reflow process. Only the portion that will become the soldering portion 14 may be immersed in the surface treatment solution, or the portion that will become the connection portion 13 may be masked and the entire surface may be immersed in the surface treatment solution. The surface treatment solution preferably contains phosphorus (P), and a solution containing phosphoric acid and phosphoric acid derivatives may be used. For example, a commercially available product such as Metas HB manufactured by Yuken Kogyo Co., Ltd. may be used. Since phosphorus (P) and tin (Sn) readily bond, simply immersion causes them to adsorb onto the surface of the tin plating layer, which has the effect of making it easier to dissolve tin oxide during reflow.

[0087] (Reflow Processing Process) The plated substrate 45, which has been subjected to the activation treatment after forming the plating layer as described above, is subjected to reflow processing. In the case of a long, narrow sheet material (strand material) wound on a roll, this reflow processing is carried out by running the sheet material in the length direction and passing it through a reflow oven while continuously performing the above-mentioned pretreatment and plating treatment. However, in the case of the plated substrate 45 of this embodiment, it is a punched material that has been punched out in advance as a terminal chain of a predetermined length as shown in Figure 1 by a press. After the above-mentioned pretreatment and plating treatment is applied to this punched material, the plated substrate 45 is supplied to a relatively small reflow oven and subjected to reflow processing.

[0088] This reflow process is performed by heating the plated substrate 45 above the melting point of tin to melt the tin plating layers 43 and 44, and then cooling it.

[0089] In the connector terminal material 1 formed in this manner, coatings 22 and 23 are formed on a base material 21 on which a plurality of terminal members 10 are continuously formed. These coatings 22 and 23 consist of nickel layers 31 and 32 made of nickel or a nickel alloy, copper-tin alloy layers 33 and 34 made of a copper-tin alloy, and tin layers 35 and 36 made of tin or a tin alloy, formed in this order. As described above, coatings 22 and 24 consisting of nickel layers 31 and 32, copper-tin alloy layers 33 and 34, and tin layers 35 and 36 are formed not only on the front and back surfaces of the base material 21, but also on both sides, so that the entire surface of the base material 21 is covered with coatings 22 and 23.

[0090] During the reflow process, the copper in the copper plating layer 42 reacts with the tin in the tin plating layers 43 and 44 to form copper-tin alloy layers 33 and 34 and tin layers 35 and 36. However, some of the copper in the copper plating layer 42 may remain unreacted, resulting in a thin copper layer existing between the nickel layers 31 and 32 and the copper-tin alloy layers 33 and 34.

[0091] In the case of a pin-shaped terminal using the terminal material 1 of this embodiment, as shown in Figure 1, the connecting portion 13 that connects to the mating terminal is formed in an elongated pin shape. Therefore, not only the front and back surfaces of the terminal material 1 but also the sides may come into contact with the mating terminal. However, even in this case, since coatings 22 and 24 are formed on the entire surface of the front, back, and sides of the connecting portion 13, the performance as a connector is not impaired. Furthermore, since coatings 22 and 23 are formed on the entire surface, corrosion is less likely to occur.

[0092] Furthermore, since nickel layers 31 and 32 covering the substrate 21 are formed on the coatings 22 and 23, the diffusion of copper and other components (substrate components) from the substrate 21 at high temperatures can be prevented, thereby improving heat resistance.

[0093] Furthermore, the copper-tin alloy layers 33 and 34 and the tin layers 35 and 36 form a composite structure in which the relatively softer tin layers 35 and 36 are supported by the harder copper-tin alloy layers 33 and 34. Since the interface between them has an uneven shape, the coefficient of friction can be reduced in combination with the lubricating effect of the tin layers 35 and 36.

[0094] Furthermore, by setting the cross-sectional area ratio of the tin layers 35 and 36 to 21% to 50% for the connection portion 13 and 31% to 90% for the soldering portion 14, adhesion of the tin layer 35 is less likely to occur in the connection portion 13, reducing the coefficient of friction, and solder wettability is improved in the soldering portion 14, thus achieving both a reduction in insertion force and improved solder wettability in high-temperature, high-humidity environments.

[0095] Furthermore, the detailed configuration is not limited to that of the embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0096] Although the nickel layers 31 and 32 were set to the same thickness range in the connection portion 13 and the soldering portion 14, they may be set to different thicknesses within that range (0.15 μm or more and 4.0 μm or less). For example, by making the soldering portion 14 thicker, when exposed to a large amount of heat during soldering, a thicker nickel layer 31 can suppress thermal damage and effectively suppress the diffusion of copper (Cu) from the substrate 21.

[0097] Although the copper-tin alloy layers 33 and 34 were set to the same thickness range at the connection portion 13 and the soldering portion 14, they may be set to different thicknesses within that range.

[0098] Furthermore, in the plating process, the nickel plating layer 41 and the copper plating layer 42 were set to the same thickness for both the connection portion 13 and the soldering portion 14, but they may be set to different thicknesses, similar to the tin plating layers 43 and 44. For example, forming a thicker copper plating layer only on the soldering portion 14 is advantageous for whisker prevention, and although a copper-tin alloy layer is necessary on the soldering portion due to the thermal barrier properties created by the formation of the copper-tin alloy, the thinner the Cu thickness and the lower the pure Sn content, the better the solder wettability, and the less deterioration of solder wettability (Z.C.T) after environmental testing (accelerated testing) can be suppressed.

[0099] A rolled material made of CDA (Copper Development Association) alloy symbol C18665 with a thickness of 0.25 mm was used as the base material. After punching it into the shape of the terminal chain shown in the figure, electrolytic degreasing was performed as a pretreatment, and nickel plating, copper plating, and tin plating were applied to the surface in order. Pickling treatment was also performed between each plating and after copper plating. The conditions for electrolytic degreasing, pickling, and plating are shown in Table 1 in the order of the process, and the same conditions were used for the following examples and comparative examples. In the table, RT indicates room temperature.

[0100] In this case, for nickel plating, the thickness of the nickel plating layer was adjusted by varying the plating time in the range of 13 to 350 seconds. For copper plating, the thickness of the copper plating layer was adjusted by varying the plating time in the range of 8 to 40 seconds. For tin plating, the plating time was set in the range of 8 to 120 seconds, and during that time, a shielding plate was used to control the thickness difference between the connection part and the soldered part. In Comparative Example 4, tin plating was performed without using a shielding plate.

[0101]

[0102] After forming various plating layers in this manner, a pre-reflow activation treatment was performed. For this activation treatment, Metas HB manufactured by Yuken Kogyo Co., Ltd. was used as the surface treatment solution. The Metas HB was adjusted to a concentration of 100 ml / L, and the areas of the plated substrate that would be soldered were immersed in the surface treatment solution, heated to 50°C, for 1 to 30 seconds depending on the thickness of the tin plating layer. For comparison, samples without the activation treatment were also prepared (Comparative Example 9).

[0103] Then, the plated substrate after this pretreatment process was reflow-treated. The reflow conditions were carried out within the range described in the embodiment.

[0104] For the terminal material after reflow processing, the solubility of tin on the surface of the soldered area was confirmed, and the average thickness of each layer of the coating and the cross-sectional area ratio of the tin layer were measured.

[0105] (Confirmation of tin solubility) After reflow processing, the surface of the soldered area of ​​the terminal material (surface of the tin layer) was examined using a scanning electron microscope (SEM) at a magnification of 5000x to obtain secondary electron (SE) images and confirm whether any undissolved areas of Sn (tin) remained. This confirmation was determined by whether or not undissolved areas with a diameter of 1.0 μm or more were observed within a 20 μm × 20 μm field of view. Samples with 0 undissolved areas were classified as A, those with 20 or fewer as B, and those with more than 20 as C.

[0106] (Average thickness of each layer) When measuring the average thickness of each layer, the measurement area was defined as part A in Figure 1 for the connection part and part B in the same figure for the soldering part. Part A is the central part in the width direction at a position L1 = 2 mm (2 mm from the top edge of the paper in Figure 1) from the tip of the pin, which has a total length of L0 = 28.8 mm and corresponds to the sliding part of the terminal. Part B is the solder-wet part of the terminal and is the central part in the width direction at a position L1 × 2 = 4 mm from the side end of the connecting part (bottom edge in Figure 1) and L1 = 2 mm from the connecting position of the terminal.

[0107] The thickness of the nickel layer was measured using a fluorescent X-ray film thickness gauge (FT150) manufactured by Hitachi High-Tech Science Co., Ltd.

[0108] To determine the average thickness of the copper-tin alloy layer, each sample was cross-sectionally processed using a focused ion beam (FIB) system (model: SMI3050TB) manufactured by Seiko Instruments Inc. The formed cross-sections (parallel to the rolling direction of the substrate) were observed at a magnification of 13,000x using a scanning ion microscope (SIM). In the cross-sectional SIM image with an inclination angle of 60°, the distance a from the interface with the nickel layer to the peak of the copper-tin alloy layer, and the distance b from the interface with the nickel layer to the valley of the copper-tin alloy layer were measured at 10 arbitrary locations. After calculating the average of these distances, they were converted to actual lengths to obtain the average thickness of the copper-tin alloy layer.

[0109] (Cross-sectional area ratio of the tin layer) Five cross-sectional images of the entire connection and soldered area parallel to the rolling direction of the substrate were acquired. The acquired backscattered electron images were binarized using the image processing software image J (ver. 1.54f) so that the tin layer was black and the copper-tin alloy layer was white. After calculating the area of ​​the tin layer and the copper-tin alloy layer, the cross-sectional area ratio of the tin layer was calculated as tin layer / (tin layer + copper-tin alloy layer) × 100, and the average of the five points was taken as the measured value. Let X be the cross-sectional area ratio of the tin layer at the connection, and Y be the cross-sectional area ratio of the tin layer at the soldered area. Binarization was performed with the intensity range set to 112 out of 255.

[0110] These measurement results are shown in Table 2.

[0111]

[0112] Regarding the solubility of tin in the tin layer, Figure 5 shows the SE image of the tin layer surface, with A, B, and C in Figure 5 indicating the surface state for each evaluation (A, B, C). As can be seen from Table 2, there were no undissolved areas in the example, indicating that the tin melted well by the reflow process. In contrast, in Comparative Example 9, since no activation treatment was performed before the reflow process, many undissolved areas remained in the soldered area.

[0113] Furthermore, the coefficient of friction, contact resistance, contact resistance after thermal shock, the exposure area ratio of the copper-tin alloy layer on the tin layer surface, and the skewness Ssk of the nickel layer were measured to evaluate solder wettability.

[0114] (Coefficient of friction) For the connection part of each sample, a 60 mm long test piece was cut parallel to the rolling direction and used as a substitute for the male terminal (male terminal test piece). For the female terminal sample, all samples were the same, and the sample from Example 13 (base material: C18665 material with a plate thickness of 0.25 mm), which was not processed into a terminal shape, was cut to 60 mm x 10 mm and an embossed pattern with a radius of curvature of 1.5 mm was made in the center of the test piece. For measurement, a friction and wear tester (UMT-Tribolab) from Bruker AXS Co., Ltd. was used, and the male terminal test piece was set up horizontally, with the convex surface of the female terminal test piece in contact with a position 5 mm below part A in Figure 1, so that part A in Figure 1 is the center of the sliding part, and a load of 3 N was applied to the male terminal test piece, and it was slid for a distance of 10 mm to a position 5 mm above part A in Figure 1. Friction coefficient data was acquired at intervals of 0.013 mm of sliding distance, and the average value of the friction coefficients obtained between 0.1 mm and 10 mm of sliding distance was used as the friction coefficient value.

[0115] (Contact Resistance) Test specimens were prepared for the connection part of each sample in the same manner as for the coefficient of friction. These were heated at 150°C for 250 hours, and the contact resistance (mΩ) before and after heating was measured. For the measurement, a friction and wear tester (UMT-Tribolab) from Bruker AXS Co., Ltd. was used. The convex surface of the female test specimen was brought into contact with the horizontally positioned male terminal test specimen, and the contact resistance value when a load of 5N was applied to the male terminal test specimen was measured using the four-terminal method.

[0116] (Contact Resistance After Thermal Shock) Test specimens were prepared for the connection points of each sample in the same manner as for the coefficient of friction, and a thermal shock test was performed using a thermal shock device (TSA-73ES) manufactured by ESPEC Corporation. The thermal shock test was conducted in accordance with the test standard MIL-STD-883H METHOD 1010.8 Condition B, which is the test method standard for integrated circuits of the U.S. Department of Defense. The low temperature side was set to -55°C and the high temperature side to 125°C, with an exposure time (holding time) of 60 minutes for each, and the number of test cycles was set to 500. After this thermal shock test, a friction and wear tester (UMT-Tribolab) manufactured by Bruker AXS Corporation was used to measure the contact resistance value when a load of 5N was applied to the male terminal test specimen by bringing the convex surface of the female test specimen into contact with the male terminal test specimen which was set horizontally, using the four-terminal method.

[0117] (Solder Wettability) For solder wettability, the zero-crossing time (Z.C.T) was measured by meniscography at point B in Figure 1 of the solder joint of each sample using a weakly active flux. Each sample underwent a pressure cooker test in a high-temperature, high-humidity environment (temperature 105°C - saturated 100%RH - test time 8 hours) using an accelerated life tester (ESPEC EHS-411M), and the zero-crossing time was measured by meniscography before and after the pressure cooker test (before and after the high-temperature, high-humidity test). The zero-crossing time was measured by immersion in Sn-3Ag-0.5Cu lead-free solder at a solder bath temperature of 245°C, with an immersion speed of 2 mm / sec, an immersion depth of 5 mm from the connection point with the joint of the sample, and an immersion time of 10 sec. A solder zero-crossing time of 2 seconds or less was classified as A, a time between 2 seconds and 3 seconds was classified as B, and a time exceeding 3 seconds was classified as C. C is a failing grade.

[0118] (Ssk: Skewness) The skewness in section A of Figure 1 was measured. The tin layer was removed by immersion in an etching solution for stripping the tin plating (Raybolt L-80) to expose the underlying copper-tin alloy layer. Then, the copper-tin alloy layer was completely stripped by immersion in an etching solution for stripping the copper-tin alloy layer (a mixture of Raybolt Copper Act S-40 100g / L and sulfuric acid 80mL / L) to expose the underlying nickel layer. For this nickel layer, the skewness Ssk was calculated from the average value of 9 points measured using a Keyence Corporation laser microscope (VK-X200) under conditions of 150x objective lens (measurement field of view 96μm × 72μm) and no filter.

[0119] (Exposed area ratio of the copper-tin alloy layer) The measurement area was designated as parts A and B in the drawing, and the surface of the tin layer was observed using a SEM (JSM-7001F manufactured by JEOL Ltd.), with a magnification of 2000x, and the ratio was 0.0028 mm. 2 Backscattered electron images of the field of view were acquired. The acquired backscattered electron images were binarized using the image processing software imageJ (ver. 1.54f) so that the exposed copper-tin alloy layer on the surface appeared black and the tin layer appeared white. The exposed area ratio was calculated by determining the area of ​​the copper-tin alloy layer. Binarization was performed with the altitude range set to 112 out of 255.

[0120] These measurement results are shown in Table 3.

[0121]

[0122] In the example where the average thickness of the nickel layer was 0.15 μm or more and 4.0 μm or less, the average thickness of the copper-tin alloy layer was 0.15 μm or more and 0.8 μm or less, the cross-sectional area ratio of the tin layer in the cross-section was 21% or more and 50% or less at the connection part (cross-sectional area ratio X%), and 31% or more and 90% or less at the soldering part (cross-sectional area ratio Y%), and the difference between Y and X was 10% or more, the coefficient of friction and contact resistance were low, and the solder wettability was also good at the soldering part.

[0123] Among these, Examples 3, 5, 7, 12, and 13, which exhibited extremely low friction coefficients at the connection points, had a cross-sectional area ratio of 25% to 45% at the connection points and 45% to 75% at the soldered points. Overall, the contact resistance and solder wettability after heating were good. However, Example 3 had a relatively small average thickness of the nickel layer, resulting in slightly higher contact resistance after heating, and its Z.C.T. evaluation after the high-temperature, high-humidity test was B.

[0124] Examples 4, 8, 9, 11, and 14, which showed a slightly higher contact resistance after heating, had a lower cross-sectional area ratio of the tin layer at the connection point. Example 6, which showed a higher coefficient of friction, had a higher cross-sectional area ratio of the tin layer at the connection point.

[0125] In thermal shock tests, repeated temperature changes cause the copper-tin alloy to grow, and as a result, the pure tin in the tin plating layer is lost, increasing contact resistance and reducing durability against temperature changes. However, as shown in Table 3, the values ​​were generally low in the examples. In example 3, however, the average thickness of the nickel layer was relatively small, resulting in slightly higher contact resistance after the thermal shock test and slightly lower durability against temperature changes. Also, in examples 4, 8, 9, 11, and 14, the cross-sectional area ratio of the tin layer at the connection point was relatively low, resulting in slightly higher contact resistance against temperature changes and slightly lower durability.

[0126] Furthermore, while repeated temperature changes in this thermal shock test could potentially cause cracks or delamination due to the multi-layered structure of metal layers with different thermal expansions (nickel layer, copper-tin alloy layer, tin layer), this phenomenon did not occur in either the example or comparative example because the film thickness of each layer was thin.

[0127] In contrast, Comparative Example 1 had a nickel layer with an average thickness that was too small, resulting in high contact resistance after heating of the connection and a Z.C.T. evaluation of C after the high temperature and high humidity test, indicating low solder wettability. Comparative Example 2 had a tin layer with a cross-sectional area ratio that was too low, resulting in a high coefficient of friction at the connection. Furthermore, the cross-sectional area ratio of the tin layer at the soldering point was also low, resulting in low solder wettability after the high temperature and high humidity test. The thermal shock test results also showed that Comparative Examples 1 and 2 had poor durability against temperature changes. Comparative Example 3 had a tin layer with a cross-sectional area ratio that was too high, resulting in a high coefficient of friction at the connection. Comparative Example 4 had almost the same cross-sectional area ratio of the tin layer and the average thickness of the copper-tin alloy layer at the soldering point and the connection point, resulting in low solder wettability at the soldering point.

[0128] Comparative Example 5 had a high contact resistance after heating at the connection point because the cross-sectional area ratio of the tin layer at the connection point was too low. Also, the friction coefficient was high due to the low cross-sectional area ratio of the tin layer at the connection point. Comparative Example 6 had a high friction coefficient at the connection point because the average thickness of the copper-tin alloy layer was too small. Also, the SsK of the nickel layer was low, resulting in low barrier properties of the nickel layer against the base material components and poor solder wettability after the high temperature and high humidity test. Comparative Example 7 had a low cross-sectional area ratio of the tin layer at both the connection point and the soldering point. The contact resistance after heating was high at the connection point, and the solder wettability was low at the soldering point due to the low cross-sectional area ratio of the tin layer. Comparative Examples 5, 6, and 7 also showed poor durability against temperature changes in the thermal shock test. In Comparative Example 8, the cross-sectional area ratio of the tin layer was slightly higher at the connection point and slightly lower at the soldering point. As a result, the difference in the cross-sectional area ratio of the tin layer between the soldering point and the connection point (Y-X) was significantly negative, leading to a slightly higher coefficient of friction and slightly lower solder wettability before and after the high-temperature, high-humidity test. In Comparative Example 9, as mentioned above, no activation treatment was performed before the reflow process, resulting in a large amount of undissolved material remaining on the surface of the tin layer.

[0129] This invention can be used as a connector for connecting electrical wiring in automobiles, consumer electronics, and the like.

[0130] 1 Connector terminal material 10 Terminal component 11 Connecting component 13 Connection part 14 Soldering part 21 Base material 22 Coating for connection part 23 Coating for soldering part 31, 32 Nickel layer 33, 34 Copper-tin alloy layer 35, 36 Tin layer 41 Nickel plating layer 42 Copper plating layer 43, 44 Tin plating layer 45 Base material with plating layer

Claims

1. A coating is formed on a base material made of rolled copper or copper alloy, comprising a nickel layer made of nickel or a nickel alloy formed on the surface of the base material, a copper-tin alloy layer made of a copper-tin alloy formed on the nickel layer, and a tin layer made of tin or a tin alloy formed on the copper-tin alloy layer, and has a connecting portion for connection to the mating side and a soldering portion for soldering to the substrate, wherein the average thickness of the nickel layer is 0.15 μm or more and 4.0 μm or less, and the average thickness of the copper-tin alloy layer is 0.15 μm or more and 0.8 μm or less, and in a cross section parallel to the rolling direction of the base material, if the ratio of the cross-sectional area of ​​the tin layer to the total area of ​​the copper-tin alloy layer and the tin layer in the connecting portion is X%, and the ratio of the cross-sectional area of ​​the tin layer to the total area of ​​the copper-tin alloy layer and the tin layer in the soldering portion is Y%, then X% is 21% or more and 50%, and Y% is 31% or more and 90%. A terminal material for connectors characterized in that Y > X, and the difference between them is 10% or more.

2. The connector terminal material according to claim 1, characterized in that the soldered portion has a skewness Ssk of the nickel layer after the tin layer and the copper-tin alloy layer have been removed, which is 0 or more and 0.6 or less.

3. The connector terminal material according to claim 1 or 2, characterized in that the exposure area ratio of the copper-tin alloy layer exposed from the tin layer on the surface of the coating is 20% or more at the connection portion and less than 10% at the soldering portion.

4. A method for manufacturing a connector terminal material having a connection portion for connection to the other side and a soldering portion for soldering to a substrate, characterized in that 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 and a tin alloy are formed in this order on a substrate made of rolled copper or a copper alloy to obtain a substrate with plating layers, and then an activation treatment is performed on the portion to be soldered with an activation treatment solution containing phosphorus, followed by a reflow treatment.

5. The method for manufacturing a connector terminal material according to claim 4, characterized in that the base material has a terminal chain formed in advance by pressing, in which a plurality of terminal members are connected.

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