Coated copper terminal material and method for producing same

Abstract

Provided is a copper terminal material with a film, which prevents the occurrence of adhesion when used as a connector, and which stably reduces the insertion / extraction force. A film is formed on a substrate comprising copper or a copper alloy, a tin layer comprising tin or a tin alloy having an average thickness of 0.2 [mu] m to 2.0 [mu] m is provided on the surface of the film, the arithmetic mean curvature (Spc) of the peak points of the surface of the film is 10 mm-1 to 70 mm-1, and the standard deviation / average value of the Spc when 10 fields of view are measured is 30% or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a coated copper terminal material useful as a terminal for a connector used in connection of electrical wiring of an automobile or a civil equipment, and the like, and a manufacturing method thereof. This application claims priority based on Patent Application No. 2023-049742 filed in Japan on March 27, 2023, and Patent Application No. 2024-23852 filed on the same day as the present application, and incorporates the contents thereof by reference. BACKGROUND

[0002] As a coated copper terminal material, there is a terminal material in which, after a copper (Cu) plating layer and a tin (Sn) plating layer are formed on a base material composed of a copper alloy, reflow soldering treatment is performed in order to suppress generation of whiskers, whereby a copper-tin (CuSn) alloy layer is formed under the tin layer of the surface layer. The connection reliability of this coated copper terminal material is high, and it can be manufactured inexpensively, so it is widely used as a terminal material.

[0003] For example, in Patent Literature 1, there is disclosed a conductive material in which a Cu-Sn alloy cladding layer mainly composed of a Cu6Sn5 phase and a Sn cladding layer are formed in this order on the surface of a base material composed of a Cu alloy strip. This conductive material is manufactured by roughening the surface of the base material to a surface roughness in which the arithmetic average roughness Ra in at least one direction is 0.15 μm or more and the arithmetic average roughness Ra in all directions is 4.0 μm or less, and after a Cu plating layer and a Sn plating layer are formed in this order on the surface of the base material, reflow soldering treatment is performed.

[0004] In Patent Literature 2, there is disclosed a Sn plated material in which a topmost layer composed of a Cu-Sn alloy layer and a Sn layer is formed on the surface of a base layer on a base material composed of copper or a copper alloy, in which the Cu-Sn alloy layer is composed of a plurality of grains of a Cu-Sn alloy, and the Sn layer is adjacent on the topmost surface and is located in a recess between the grains of the Cu-Sn alloy. It is described that in this Sn plated material, the area ratio of the Sn layer 16 on the topmost surface is 20 to 80%, and the maximum thickness of the Sn layer 16 is smaller than the average grain size of the grains of the Cu-Sn alloy.

[0005] However, since the tin layer (Sn layer) is relatively soft, it is easy to adhere between the contacts each other, and since the contact area between the contacts becomes large, the frictional force when the connector is inserted becomes too large, and there is a problem that it is difficult to insert in a multi-pin terminal or the like.

[0006] Patent Document 3 discloses a plated material comprising a base layer of, for example, Ni on a conductive substrate, an intermediate layer of copper or a copper alloy on the base layer, and an outermost layer of a Cu-Sn intermetallic compound on the intermediate layer. The material states that, since the outermost layer of this plated material is composed of a hard Cu-Sn intermetallic compound layer, fretting is less likely to occur even when the contact pressure between terminals is reduced.

[0007] However, when the outermost layer is a Cu—Sn intermetallic compound layer, copper (Cu) diffuses at high temperatures and copper oxide is easily formed on the surface.

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-077307

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2015-180770

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. 2007-247060 Summary of the Invention

[0011] The present invention has been made in view of such circumstances, and an object thereof is to provide a coated copper terminal material that prevents sticking when used as a connector and stably reduces insertion and extraction force.

[0012] The copper terminal material with coating of the present invention comprises a base material composed of copper or a copper alloy and a coating formed on the base material, wherein the surface of the coating has a tin layer composed of tin or a tin alloy with an average thickness of 0.2 μm or more and 2.0 μm or less, and the arithmetic mean curvature Spc of the peak vertex of the surface of the coating is 10 mm. -1 Above and 70mm -1 The standard deviation / average value (CV value) of the arithmetic mean curvature Spc of the peak apex when 10 visual fields are measured is 30% or less.

[0013] Since the surface of the coated copper terminal material is composed of a tin layer, it has the good electrical properties originally possessed by the tin layer. If the average thickness of the tin layer is less than 0.2 μm, Cu diffuses at high temperatures and easily forms Cu oxides on the surface, thereby increasing contact resistance. If it exceeds 2.0 μm, the insertion and removal force when used as a connector increases due to the soft tin layer, making it difficult to achieve a reduction in the insertion and removal force associated with the multi-pin configuration of the connector. The average thickness of the tin layer is preferably greater than 0.3 μm and less than 1.8 μm.

[0014] By setting the arithmetic mean curvature Spc of the peak apex of the coating surface to 10 mm -1 Above and 70mm -1The dynamic friction coefficient can be reduced, and by setting the standard deviation / average of Spc when 10 fields of view are measured to be 30% or less, the dynamic friction coefficient is stable, and local variation is also suppressed.

[0015] The arithmetic mean curvature of the peak apex, Spc, is prescribed by ISO-25178, and the greater the value, the more pointed the points in contact with the mating terminal. If Spc is less than 10 mm -1 , it is close to flat, so the contact area when the connector comes into contact with the mating terminal becomes large, and thus the dynamic friction coefficient increases. If Spc exceeds 70 mm -1 , the surface becomes too steep, and thus warping of the mating terminal occurs. If the standard deviation / average of Spc exceeds 30%, the dynamic friction coefficient is unstable due to local variation.

[0016] Spc is more preferably 20 mm -1 or more and 60 mm -1 or less.

[0017] In the copper terminal material with a coating film of the present application, the coating film preferably has a copper-tin alloy layer composed of an alloy of copper and tin below the tin layer. The average thickness of the copper-tin alloy layer is preferably 0.2 μm or more and 2.5 μm or less.

[0018] In the copper terminal material with a coating film of the present application, the coating film can have a nickel layer in contact with the substrate and composed of nickel or a nickel alloy.

[0019] The nickel layer can prevent diffusion of copper from the substrate and improve heat resistance. The average thickness of this nickel layer is preferably 0.05 μm or more and 1.0 μm or less.

[0020] The manufacturing method of the copper terminal material with a coating film of the present application includes a plating step of forming a plated material on the substrate, the plated material being formed by forming a plated layer having a tin plating layer composed of tin or a tin alloy on the surface, and a reflow soldering step of heating the plated material to perform reflow soldering processing. The thickness of the tin plating layer in the plating step is 0.2 μm or more and 3.0 μm or less. The reflow soldering processing includes a heating step of heating the plated material to a peak temperature of 240°C or more and 300°C or less, a first cooling step of passing the plated material through a cooling furnace in which the furnace temperature is 20°C or more and 70°C or less after the heating step so that the material of the plated material reaches a temperature of 150°C or more and 220°C or less, and a second cooling step of cooling after the first cooling at a cooling rate of 100°C / sec or more and 300°C / sec or less. In the first cooling step, the plated material is passed through the cooling furnace at 10 m 3 / minute or more and 300 m 3cooling air of 10 m

[0021] If the thickness of the tin plating layer composed of tin or tin alloy is less than 0.2 μm or more than 3.0 μm, the average thickness of the tin layer after the reflow soldering process becomes less than 0.2 μm or more than 2.0 μm, and the desired tin layer cannot be obtained.

[0022] If the peak temperature of the heating process is less than 240°C, the tin does not uniformly melt, and if the peak temperature exceeds 300°C, copper of the base material diffuses to the tin plating layer, a gap is formed at the interface between the base material and the tin layer, and the tin layer can peel off, and thus is not preferred.

[0023] In the cooling process of the reflow soldering process, a primary cooling process is provided in which the plated material is passed through a cooling furnace having an internal temperature of 20°C or higher and 70°C or lower to bring the material of the plated material to a material reaching temperature of 150°C or higher and 220°C or lower, and is cooled to a temperature below the melting point of tin, and then in a secondary cooling process, rapid cooling is performed at a large cooling rate.

[0024] In the primary cooling process, by spraying a prescribed cooling air to the surface of the plated material in a cooling furnace having a prescribed internal temperature, the surface shape can be appropriately controlled at a temperature below the melting point of tin, and thus the arithmetic mean curvature Spc of the peak top of the plated film surface is set to 10 mm -1 or higher and 70 mm -1 Hereinafter, the standard deviation / average value (CV value: coefficient of variation) of Spc when 10 fields of view are measured is set to 30% or lower.

[0025] In this case, if the internal temperature of the cooling furnace is less than 20°C, the Spc and the CV value (standard deviation / average value) of Spc become too large due to the excessively fast cooling rate, and Spc cannot be set to 70 mm -1 or lower, and the CV value (standard deviation / average value) of Spc cannot be set to 30% or lower. If the internal temperature exceeds 70°C, the cooling time to a temperature below the melting point of tin is excessively long, and thus the CV value (standard deviation / average value) of Spc becomes too large.

[0026] If the material reaching temperature of the plated material is less than 150°C, the cooling time is excessively long, and thus the CV value (standard deviation / average value) of Spc becomes too large. If the material reaching temperature exceeds 220°C, the tin is secondarily cooled in a semi-molten state, and thus the CV value (standard deviation / average value) of Spc becomes too large. The material reaching temperature is preferably 160°C or higher and 210°C or lower, and further preferably 170°C or higher and 200°C or lower.

[0027] If the cooling air amount is less than 10 m 3 / minute, Spc becomes too small due to insufficient cooling, and cannot be set to 10 mm -1 On the other hand, if the cooling air volume exceeds 300 m 3 / minute, molten tin flows due to a large amount of air blowing, and Spc and the CV value (standard deviation / average value) of Spc become too large. The temperature of the cooling air is preferably 30°C or higher and 60°C or lower.

[0028] Next, rapid cooling is performed by a secondary cooling step, and a desired surface shape is achieved. If the cooling speed of this secondary cooling step is less than 100°C / sec, the desired surface shape cannot be obtained. It is difficult to set the cooling speed to more than 300°C / sec.

[0029] In the production method of the copper terminal material with a coating film of the present application, the tin plating layer can be formed after the copper plating layer composed of copper or copper alloy is formed on the base material in the plating step.

[0030] In the case where the copper plating layer is formed, the temperature increase rate of the plated material in the heating step is preferably 20°C / sec or higher and 75°C / sec or lower. If the temperature increase rate is less than 20°C / sec, during the period until tin is molten, copper atoms preferentially diffuse in the grain boundaries of tin, and copper-tin intermetallic compounds grow abnormally near the grain boundaries, and thus the desired copper-tin alloy layer cannot be obtained. On the other hand, if the temperature increase rate exceeds 75°C / sec, the growth of copper-tin intermetallic compounds is insufficient, and thus the desired copper-tin alloy layer still cannot be obtained.

[0031] In addition, in the case where the copper plating layer is formed, if the peak temperature of the heating step is less than 240°C, tin does not uniformly melt, and if the peak temperature exceeds 300°C, copper-tin intermetallic compounds grow sharply, and the unevenness of the copper-tin alloy layer becomes large, and thus is not preferable. Furthermore, if the cooling speed of the secondary cooling step is less than 100°C / sec, the growth of copper-tin intermetallic compounds is caused, and thus the desired copper-tin alloy layer cannot be obtained.

[0032] In the production method of the copper terminal material with a coating film of the present application, it is preferable that a nickel plating layer composed of nickel or nickel alloy is formed on the surface of the base material in the plating step.

[0033] According to the present application, it is possible to provide a copper terminal material with a coating film, in which the arithmetic mean curvature Spc of the peak apex of the surface of the tin layer forming the surface of the terminal material is set to 10 mm -1 or higher and 70 mm -1 or lower, and the standard deviation / average value of Spc when 10 fields of view are measured is set to 30% or lower, adhesion when used as a connector is prevented, and the dynamic friction coefficient is reduced and stabilized, and thus the insertion and extraction force is stably reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a cross-sectional view schematically showing a first embodiment of the coated copper terminal material of the present invention.

[0035] Figure 2 Yes Figure 1 A cross-sectional view of the plated material during the manufacturing process of the coated copper terminal material.

[0036] Figure 3 This is a cross-sectional view schematically showing a second embodiment of the coated copper terminal material of the present invention.

[0037] Figure 4 Yes Figure 3 A cross-sectional view of the plated material during the manufacturing process of the coated copper terminal material.

[0038] Figure 5 This is a cross-sectional view schematically showing a third embodiment of the coated copper terminal material of the present invention.

[0039] Figure 6 Yes Figure 5 A cross-sectional view of the plated material during the manufacturing process of the coated copper terminal material.

[0040] Figure 7 This is a cross-sectional view schematically showing a fourth embodiment of the coated copper terminal material of the present invention.

[0041] Figure 8 Yes Figure 7 A cross-sectional view of the plated material during the manufacturing process of the coated copper terminal material. DETAILED DESCRIPTION

[0042] An embodiment of the coated copper terminal material of the present invention will be described.

[0043] (First embodiment)

[0044] like Figure 1 As shown, the coated copper terminal material 1 of the first embodiment has a coating 5 formed by laminating a tin layer 3 composed of tin or a tin alloy on a base material 2 composed of copper or a copper alloy.

[0045] The substrate 2 is a strip material formed into a strip shape, and its composition is not particularly limited as long as the surface is made of copper or a copper alloy.

[0046] The tin layer 3 is formed by forming a plating layer made of tin or a tin alloy on the base material 2 and then performing a reflow process.

[0047] The average thickness of the tin layer 3 is between 0.2 μm and 2.0 μm. The lubricity of the tin layer 3 keeps the connector insertion and removal forces low and reduces contact resistance, thereby exhibiting excellent electrical properties. However, if the average thickness is less than 0.2 μm, the excellent properties of tin are difficult to achieve. Furthermore, solderability and corrosion resistance may be reduced.

[0048] On the other hand, if the average thickness of the tin layer 3 exceeds 2.0 μm, it is soft and easily adheres, which increases the insertion and removal force when used as a connector, making it difficult to reduce the insertion and removal force associated with the increase in the number of pins in the connector. The average thickness of the tin layer 3 is preferably 0.3 μm to 1.8 μm.

[0049] The arithmetic mean curvature Spc (hereinafter sometimes referred to as Spc) of the peak top of the surface of the tin layer 3 is 10 mm -1 Above and 70mm -1 The standard deviation / average value (coefficient of variation) of Spc when measuring 10 visual fields is 30% or less.

[0050] The arithmetic mean curvature Spc of the peak is specified by ISO-25178. The larger the value, the sharper the point of contact with other objects. If Spc is less than 10mm -1 , it is close to flat, so the contact area when the connector contacts the mating terminal becomes larger, and the dynamic friction coefficient increases.

[0051] If Spc exceeds 70mm -1 If the standard deviation / average value of Spc exceeds 30%, the dynamic friction coefficient will fluctuate locally and become unstable. Spc is more preferably 20mm -1 Above and 60mm -1 Hereinafter, the standard deviation / average value of Spc is more preferably 25% or less.

[0052] The manufacturing method of the copper terminal material 1 with film formed as above is described. The copper terminal material 1 with film is plated with tin or tin alloy on a substrate 2. Figure 2 As shown, the plated material 7 is formed by laminating the tin plating layer 4 on the base material 2 and then performing a reflow process.

[0053] A plate material made of copper or a copper alloy is prepared as the base material 2 , and the surface of the plate material is cleaned by performing treatments such as degreasing and pickling.

[0054] As the plating bath for tin plating, a general tin plating bath can be used, and for example, a sulfuric acid bath in which sulfuric acid (H2SO4) and stannous sulfate (SnSO4) are main components can be used. The temperature of the plating bath is 15 to 35°C, and the current density is 1 to 30 A / dm 2 . The film thickness of the tin plating layer 4 is 0.2 μm or more and 3.0 μm or less.

[0055] If the thickness of the tin plating layer 4 is less than 0.2 μm or exceeds 3.0 μm, the average thickness of the tin layer 3 after the reflow soldering process becomes less than 0.2 μm or exceeds 2.0 μm, and the desired tin layer 3 cannot be obtained.

[0056] In the reflow soldering process, the plated material 7 is heated to temporarily melt the tin plating layer 4, and then rapidly cooled. Specifically, a process including the following steps is provided: a heating step in which the plated material 7 is heated to a temperature of 240°C or higher and 300°C or lower, which is higher than the melting point of tin, in a heating furnace provided with a CO reducing atmosphere; a first cooling step in which the plated material 7 is passed through a cooling furnace provided with a temperature of 20°C or higher and 70°C or lower in the furnace to bring the material of the plated material 7 to a temperature of 150°C or higher and 220°C or lower; and a second cooling step in which the material is cooled at a cooling rate of 100°C / sec or higher and 300°C / sec or lower after the first cooling.

[0057] In this case, in the first cooling step, cooling air is sprayed to the surface of the plated material 7 at an air volume of 10 m 3 / minute or higher and 300 m 3 / minute or lower. The temperature of the cooling air is preferably 30°C or higher and 60°C or lower.

[0058] By performing the heating step in a reducing atmosphere, a tin oxide film having a high melting temperature is prevented from being formed on the surface of the tin plating layer 4, and the reflow soldering process can be performed at a lower temperature and in a shorter time.

[0059] If the peak temperature of the heating step is less than 240°C, tin is not uniformly melted, and thus this is not preferable. Also, if the peak temperature exceeds 300°C, copper of the base material 2 diffuses to the tin plating layer 4, a gap is formed at the interface between the base material 2 and the tin layer 3, and the tin layer can be peeled off, and thus this is not preferable.

[0060] The cooling step after the heating is provided in two stages. In the first cooling step in which the plated material 7 is passed through a cooling furnace provided with a temperature of 20°C or higher and 70°C or lower in the furnace to bring the material of the plated material 7 to a temperature of 150°C or higher and 220°C or lower, the material is cooled to a temperature below the melting point of tin, and then in the second cooling step, the material is rapidly cooled at a greater cooling rate.

[0061] In the primary cooling step, a prescribed cooling air is sprayed to the surface of the plated material 7 in a cooling furnace having a prescribed furnace temperature, whereby the surface shape is appropriately controlled at a temperature below the melting point of tin. Thereby, the arithmetic mean curvature SPC of the peak apex of the surface of the coating film 5 (tin layer 3) can be set to 10 mm -1 or more and 70 mm -1 Hereinafter, the standard deviation / average (CV value) of SPC when 10 fields of view are measured is set to 30% or less.

[0062] In this case, if the furnace temperature of the cooling furnace is less than 20°C, SPC and the CV value (standard deviation / average) of SPC become too large due to the excessively fast cooling speed, and SPC cannot be set to 70 mm -1 or more, and the CV value (standard deviation / average) of SPC cannot be set to 30% or less. If the furnace temperature exceeds 70°C, the cooling time until the temperature below the melting point of tin is reached is excessively long, and thus the CV value (standard deviation / average) of SPC becomes too large.

[0063] If the material of the plated material 7 reaches a temperature of less than 150°C in the primary cooling step, the cooling time is excessively long, and thus the CV value (standard deviation / average) of SPC becomes too large. If the temperature of the plated material 7 is not reduced to 220°C or less in the primary cooling step, tin is secondarily cooled in a semi-molten state, and thus the CV value (standard deviation / average) of SPC becomes too large. The material of the plated material 7 in the primary cooling step preferably reaches a temperature of 160°C or more and 210°C or less, and further preferably 170°C or more and 200°C or less.

[0064] If the air volume of the cooling air in the primary cooling step is less than 10 m 3 / minute, SPC becomes too small due to insufficient cooling, and cannot be set to 10 mm -1 or more. On the other hand, if the air volume of the cooling air exceeds 300 m 3 / minute, the molten tin flows due to the large amount of air blowing, and thus SPC and the CV value (standard deviation / average) of SPC become too large.

[0065] In addition, the cooling air is vertically sprayed to the plated material 7 from a height position of about 10 cm from the surface of the plated material 7.

[0066] Next, the plated material 7 is rapidly cooled in the secondary cooling step, and a desired surface shape is achieved. If the cooling speed of this secondary cooling step is less than 100°C / sec, the desired surface shape cannot be obtained. It is difficult to set the cooling speed to exceed 300°C / sec.

[0067] The film 5 of the copper terminal material 1 with film thus produced has good electrical properties of tin as the surface thereof is composed of the tin layer 3. Further, the arithmetic mean curvature Spc of the peak apex of the surface of the film 5 (tin layer 3) is 10 mm -1 and 70 mm -1 Therefore, the dynamic friction coefficient can be reduced.

[0068] Further, by setting the standard deviation / average of Spc at the time of measurement of 10 fields of view to 30% or less, the dynamic friction coefficient is stabilized, and local variation is also suppressed.

[0069] Therefore, by using the copper terminal material 1 with film as a terminal material of a connector, the insertion and extraction force can be stably reduced, and adhesion between the terminal material and a mating terminal can be prevented.

[0070] (Second Embodiment)

[0071] As shown in Figure 3 In the copper terminal material 1 with film of the second embodiment, the film 12 provided on the base material 2 is composed of a copper-tin alloy layer 13 composed of an alloy of copper and tin and a tin layer 14, in this order. In other words, the film 12 has the copper-tin alloy layer 13 below the tin layer 14.

[0072] As described later, the copper-tin alloy layer 13 and the tin layer 14 are formed by performing reflow soldering after sequentially performing copper plating composed of copper or a copper alloy and tin plating composed of tin or a tin alloy on the base material 2.

[0073] The copper-tin alloy layer 13 is formed to have an average thickness of 0.2 μm or more and 2.5 μm or less. If the thickness thereof is less than 0.2 μm, the contact resistance can increase in a high-temperature environment. If the thickness thereof exceeds 2.5 μm, the copper-tin alloy layer 13 is hard, and thus can become a cause of crack generation at the time of bending processing. The average grain diameter of the copper-tin alloy layer 13 is preferably 0.2 μm or more and 1.5 μm or less.

[0074] The copper-tin alloy layer 13 is composed of a Cu3Sn layer 15 of the lower layer and a Cu6Sn5 layer 16 disposed on the Cu3Sn layer 15. The Cu3Sn layer 15 is locally formed on the surface of the base material 2, and thus the Cu6Sn5 alloy layer 16 is formed on both the Cu3Sn alloy layer 15 on the base material 2 and the upper portion of the base material 2 in which the Cu3Sn alloy layer 15 is not present.

[0075] As in the first embodiment, the average thickness of the tin layer 14 is 0.2 μm or more and 2.0 μm or less. If the thickness of the tin layer 14 is less than 0.2 μm, copper diffuses at high temperatures and thus the oxide of copper is easily formed on the surface, and thus the contact resistance increases, which can result in a decrease in connection reliability. Further, the solderability and corrosion resistance can also decrease.

[0076] On the other hand, if the average thickness of the tin layer 14 exceeds 2.0 μm, the effect of hardening the base of the surface of the copper-tin alloy layer 13 present in the lower layer of the soft tin layer 14 is weakened, the plugging force when used as a connector increases, and it is difficult to achieve a reduction in the plugging force accompanying the multi-needling of the connector. The average thickness of the tin layer 14 is preferably 0.3 μm or more and 1.8 μm or less.

[0077] As with the first embodiment, the arithmetic mean curvature Spc of the peak apex of the surface of the tin layer 14 is 10 mm -1 or more and 70 mm -1 or less.

[0078] The arithmetic mean curvature Spc of the peak apex is prescribed by ISO-25178, and the larger the value, the more pointed the points of contact with other objects are. If Spc is less than 10 mm -1 , the surface is close to flat, and thus the contact area when the connector comes into contact with the mating terminal increases, and thus the dynamic friction coefficient increases. If Spc exceeds 70 mm -1 , the surface roughness becomes too steep, and thus warping of the mating terminal occurs.

[0079] If the standard deviation / average value of Spc exceeds 30%, the dynamic friction coefficient becomes unstable due to local variations. Spc is more preferably 20 mm -1 or more and 60 mm -1 or less.

[0080] A method of manufacturing the copper terminal material 11 with a coating film as constructed above will be described. The copper terminal material 11 with a coating film is formed by sequentially performing copper plating composed of copper or a copper alloy and tin plating composed of tin or a tin alloy on the base material 2, as shown in the drawing, and is formed after the plated material 19 in which the copper plated layer 17 and the tin plated layer 18 are stacked on the base material 2 is formed by performing reflow soldering processing. Figure 4

[0081] A plate material composed of copper or a copper alloy is prepared as the base material 2, and the surface is cleaned by performing degreasing, pickling, and the like on the plate material.

[0082] The copper plating processing can use a general copper plating bath, and for example, a copper sulfate bath in which copper sulfate (CuSO4) and sulfuric acid (H2SO4) are main components or the like can be used. The temperature of the plating bath is 20 to 50°C, and the current density is 1 to 50 A / dm 2 . The film thickness of the copper plated layer 17 formed by the copper plating is 0.05 μm or more and 0.50 μm or less.

[0083] ​As the plating bath for tin plating, a general tin plating bath can be used, and for example, a sulfuric acid bath in which sulfuric acid (H2SO4) and stannous sulfate (SnSO4) are main components can be used. The temperature of the plating bath is 15 to 35°C, and the current density is 1 to 30 A / dm2. 2 The film thickness of the tin plating layer 18 is 0.2 μm or more and 3.0 μm or less.

[0084] If the thickness of the tin plating layer 18 is less than 0.2 μm or exceeds 3.0 μm, the average thickness of the tin layer 14 after the reflow soldering process becomes less than 0.2 μm or exceeds 2.0 μm, and the desired tin layer 14 cannot be obtained.

[0085] By carrying out these plating processes, a plated material 19 in which the copper plating layer 17 and the tin plating layer 18 are sequentially stacked on the base material 2 is formed.

[0086] In the reflow soldering process, the plated material 19 is heated to temporarily melt the copper plating layer 17 and the tin plating layer 18, and then is rapidly cooled. Specifically, a process including the following steps is provided: a heating step in which the plated material 19 is heated to a temperature of 240°C or more and 300°C or less at a temperature increasing rate of 20°C / sec or more and 75°C / sec or less in a heating furnace set to a CO reducing atmosphere; a first cooling step in which, after the heating step, the plated material 19 is passed through a cooling furnace in which the temperature is 20°C or more and 70°C or less to bring the material of the plated material to a temperature of 150°C or more and 220°C or less; and a second cooling step in which, after the first cooling, cooling is performed at a cooling rate of 100°C / sec or more and 300°C / sec or less.

[0087] In this case, in the first cooling step, cooling air is sprayed to the surface of the plated material 19 at an air volume of 10 m 3 / minute or more and 300 m 3 / minute or less. The temperature of the cooling air is preferably 30°C or more and 60°C or less.

[0088] By carrying out the heating step in a reducing atmosphere, the formation of a tin oxide film having a high melting temperature on the surface of the tin plating layer 18 can be prevented, and the reflow soldering process can be performed at a lower temperature and in a shorter time, and the desired copper-tin alloy structure can be easily produced.

[0089] If the temperature increasing rate in the heating step is less than 20°C / sec, during the period until the tin is melted, copper atoms preferentially diffuse in the grain boundaries of the tin, and copper-tin intermetallic compounds abnormally grow in the vicinity of the grain boundaries, and thus the desired copper-tin alloy layer 13 cannot be obtained. On the other hand, if the temperature increasing rate exceeds 75°C / sec, the growth of the copper-tin intermetallic compounds is insufficient, and thus the desired copper-tin alloy layer cannot be obtained.

[0090] If the peak temperature of the heating step is less than 240°C, tin does not uniformly melt, and if the peak temperature exceeds 300°C, copper-tin intermetallic compounds grow sharply, the unevenness of the copper-tin alloy layer 13 becomes large, and thus is not preferable.

[0091] In the primary cooling step, a prescribed cooling air is sprayed to the surface of the plated material 19 in a cooling furnace having a prescribed furnace temperature, whereby the surface shape is appropriately controlled at a temperature below the melting point of tin. Thus, the arithmetic mean curvature SPC of the peak points of the surface of the coating film 12 can be set to 10 mm -1 or more and 70 mm -1 or less.

[0092] In this case, if the furnace temperature of the cooling furnace is less than 20°C, SPC and the CV value (standard deviation / average value) of SPC become too large due to the excessively fast cooling speed, and SPC cannot be set to 70 mm -1 or less. If the furnace temperature exceeds 70°C, the cooling time until the temperature below the melting point of tin is reached is excessively long, and thus the CV value (standard deviation / average value) of SPC becomes too large.

[0093] If the material of the plated material 19 reaches a temperature of less than 150°C in the primary cooling step, the cooling time is excessively long, and thus the CV value (standard deviation / average value) of SPC becomes too large. If the temperature of the plated material 19 in the primary cooling step is not reduced to 220°C or less, tin is secondarily cooled in a semi-melted state, and thus the CV value (standard deviation / average value) of SPC becomes too large. The material of the plated material 19 in the primary cooling step preferably reaches a temperature of 160°C or more and 210°C or less, and further preferably 170°C or more and 200°C or less.

[0094] If the air volume of the cooling air in the primary cooling step is less than 10 m 3 / minute, SPC becomes too small due to insufficient cooling, and cannot be set to 10 mm -1 or more. On the other hand, if the air volume of the cooling air exceeds 300 m 3 / minute, the molten tin flows due to the large amount of air blowing, and thus SPC and the CV value (standard deviation / average value) of SPC become too large.

[0095] In addition, the cooling air is sprayed vertically to the plated material 19 from a height position of about 10 cm from the surface of the plated material 19.

[0096] Next, the plated material 19 is rapidly cooled in a secondary cooling process, and a desired surface shape is achieved. If the cooling speed in the secondary cooling process is less than 100°C / sec, copper-tin intermetallic compounds excessively grow, and thus a desired copper-tin alloy layer cannot be obtained. It is difficult to set the cooling speed to more than 300°C / sec.

[0097] In the film 12 of the copper terminal material 11 with film thus produced, the copper-tin alloy layer 13 and the tin layer 14 form a composite structure through an interface of a concave-convex shape, the relatively soft tin layer 14 is supported by the harder copper-tin alloy layer 13, and the arithmetic mean curvature Spc of the peak apexes of the surface of the film 12 is 10 mm -1 or more and 70 mm -1 Therefore, the dynamic friction coefficient can be reduced.

[0098] Further, by setting the standard deviation / average value of Spc when 10 fields of view are measured to be 30% or less, the dynamic friction coefficient is stabilized, and local variation is also suppressed.

[0099] Therefore, by using the copper terminal material 11 with film as a terminal material of a connector, the insertion and extraction force can be stably reduced, and adhesion between the terminal material and a mating terminal can be prevented.

[0100] (Third Embodiment)

[0101] As Figure 5 shown, in the copper terminal material 21 with film of the third embodiment, the film 22 has a nickel layer 23 that is in contact with the base material 2 and is composed of nickel or a nickel alloy, and a tin layer 24 that is laminated on the nickel layer 23 and is composed of tin or a tin alloy. In other words, the film 22 has the nickel layer 23 below the tin layer 24.

[0102] By having the nickel layer 23, copper diffusion from the base material 2 to the film 22 can be prevented, and thus heat resistance can be improved.

[0103] The average thickness of the nickel layer 23 is 0.05 μm or more and 1.0 μm or less. This is because, if it is less than 0.05 μm, the effect of preventing copper diffusion from the base material 2 is reduced, and if it exceeds 1.0 μm, it can be difficult to perform bending processing and the like.

[0104] The arithmetic mean curvature Spc of the peak apexes of the surface of the tin layer 24 is 10 mm -1 or more and 70 mm -1 Further, the standard deviation / average value of Spc when 10 fields of view are measured is 30% or less, which is the same as in the first embodiment.

[0105] The Spc of the surface of the tin layer 24 is more preferably 20 mm -1 or more and 60 mm -1The standard deviation / average value of the SPC is more preferably 25% or less.

[0106] The copper terminal material 21 with the coating film thus configured is formed by sequentially performing nickel plating consisting of nickel or a nickel alloy and tin plating consisting of tin or a tin alloy on the base material 2, like Figure 6 As shown, the plated material 27 formed by laminating the nickel plating layer 25 and the tin plating layer 26 on the base material 2 is formed by performing reflow soldering treatment thereafter.

[0107] The nickel plating treatment for forming the nickel plating layer 25 can use a general nickel plating bath, and for example, a sulfuric acid bath using sulfuric acid (H2SO4) and nickel sulfate (NiSO4) as main components can be used. The temperature of the plating bath is 20°C or higher and 60°C or lower, the current density is 5 to 60 A / dm 2 The film thickness of the nickel plating layer 25 is 0.05 μm or more and 1.0 μm or less.

[0108] The conditions of the tin plating and the conditions of the reflow soldering treatment are the same as those described in the first embodiment.

[0109] The copper terminal material 21 with the coating film thus manufactured has the nickel layer 23, and thus can prevent the diffusion of copper, thereby improving heat resistance.

[0110] (Fourth Embodiment)

[0111] In the copper terminal material 21 with the coating film of the fourth embodiment, as shown in Figure 7 The coating film 32 has a nickel layer 33 which is in contact with the base material 2 and consists of nickel or a nickel alloy, a copper-tin alloy layer 34 which is laminated on the nickel layer 33 and consists of an alloy of copper and tin, and a tin layer 35 which is laminated on the copper-tin alloy layer 34 and consists of tin or a tin alloy. In other words, the coating film 32 has the tin layer 35 on the surface, the copper-tin alloy layer 34 below the tin layer 35, and the nickel layer 33 below the copper-tin alloy layer 34 which is in contact with the base material 2.

[0112] By providing the nickel layer 33, the diffusion of copper of the base material 2 to the coating film 32 can be prevented, thereby improving heat resistance.

[0113] The average thickness of the nickel layer 33 is 0.05 μm or more and 1.0 μm or less. This is because, if less than 0.05 μm, the effect of preventing the diffusion of copper from the base material 2 is reduced, and if more than 1.0 μm, it can be difficult to perform bending processing and the like.

[0114] The copper-tin alloy layer 34 is composed of a Cu3Sn alloy layer 36 which is formed locally on the base material 2 side and a Cu6Sn5 alloy layer 37 which is formed so as to cover the upper side thereof. Therefore, the Cu6Sn5 alloy layer 37 is formed so as to cover both the upper side of the Cu3Sn alloy layer 36 on the nickel layer 33 and the upper side of the nickel layer 33 where the Cu3Sn alloy layer 36 is not present.

[0115] The average thickness of the copper-tin alloy layer 34 is preferably 0.2 μm or more and 2.5 μm or less, and the average grain diameter is 0.2 μm or more and 1.5 μm or less. The average thickness of the tin layer 35 is 0.2 μm or more and 2.0 μm or less.

[0116] As in the first embodiment, the arithmetic mean curvature Spc of the peak apex of the surface of the tin layer 35 is 10 mm -1 or more and 70 mm -1 or less. The Spc is more preferably 20 mm -1 or more and 60 mm -1 or less. The Spc is more preferably 25% or less in terms of the standard deviation / average value.

[0117] The copper terminal material with a coating 31 thus configured is formed by sequentially performing nickel plating composed of nickel or a nickel alloy, copper plating composed of copper or a copper alloy, and tin plating composed of tin or a tin alloy on the base material 2, as shown in Figure 8 The plated material 44 in which the nickel plating layer 41, the copper plating layer 42, and the tin plating layer 43 are stacked on the base material 2 is formed, and then reflow soldering treatment is performed to form the copper terminal material with a coating 31.

[0118] The conditions for the nickel plating, the copper plating, and the tin plating are the same as those described in the first to third embodiments.

[0119] The copper terminal material with a coating 31 is formed by performing reflow soldering treatment on the plated material 44 in which the nickel plating layer 41, the copper plating layer 42, and the tin plating layer 43 are formed. The reflow soldering treatment is the same as that in the second embodiment, and thus the description thereof is omitted.

[0120] The copper terminal material with a coating 31 thus produced has the nickel layer 33 in the lower layer portion of the coating 32, and thus can prevent the diffusion of copper, thereby improving heat resistance. Further, the copper-tin alloy layer 34 and the tin layer 35 have an interface with a concave-convex shape, the copper-tin alloy layer 34 supports the tin layer 35, the arithmetic mean curvature of the peak apex of the surface, and the CV value when 10 fields of view are measured are within the prescribed ranges, and thus the dynamic friction coefficient is also stable and low.

[0121] Example

[0122] A copper alloy plate having a plate thickness of 0.25 mm was used as a base material, and various platings were performed under the following plating bath conditions.

[0123] (Nickel plating)

[0124] Nickel sulfate: 300 g / L

[0125] Sulfuric acid: 2 g / L

[0126] Liquid temperature: 45°C

[0127] Current density: 20 ASD (A / dm 2 )

[0128] (Copper plating)

[0129] Copper sulfate: 250 g / L

[0130] Sulfuric acid: 50 g / L

[0131] Liquid temperature: 25°C

[0132] Current density: 5 ASD

[0133] (Tin plating)

[0134] Tin sulfate: 75 g / L

[0135] Sulfuric acid: 85 g / L

[0136] Additive: 10 g / L

[0137] Liquid temperature: 25°C

[0138] Current density: 2 ASD

[0139] Plated materials in which a tin plating layer was formed on a substrate (Examples 1, 5, 9, Comparative Examples 1, 5), plated materials in which a copper plating layer and a tin plating layer were sequentially formed on a substrate (Examples 2, 6, 10, Comparative Examples 2, 6), plated materials in which a nickel plating layer and a tin plating layer were sequentially formed on a substrate (Examples 3, 7, 11, Comparative Examples 3), plated materials in which a nickel plating layer, a copper plating layer, and a tin plating layer were sequentially formed on a substrate (Examples 4, 8, 12, Comparative Examples 4, 7) were respectively prepared, and reflow soldering treatment was performed under the conditions of Tables 1 and 2.

[0140] [Table 1]

[0141]

[0142] [Table 2]

[0143]

[0144] The average thickness of the tin layer on the surface, the arithmetic average curvature of the peak top point Spc, the dynamic friction coefficient μ were measured for the obtained test samples, and the stability was evaluated.

[0145] [The average thickness of the tin layer]

[0146] The average thickness of the tin layer was measured by a fluorescent X-ray film thickness meter (SEA5120A) manufactured by SII NanoTechnology Inc.

[0147] In the sample having the copper-tin alloy layer, after the thickness of all the layers containing tin of the sample after reflow soldering was measured, the tin layer was removed to expose the underlying copper-tin alloy layer, and the thickness of the copper-tin alloy layer was measured, and (thickness of all the layers containing tin - thickness of the copper-tin alloy layer) was defined as the thickness of the tin layer. The thickness of all the layers containing tin includes the copper-tin alloy layer portion and the tin layer portion, but the tin solidification has unevenness, and thus the average thickness was calculated. As for the removal of the tin layer, the copper-tin alloy layer was immersed in a plating film peeling etching solution composed of components that do not etch the copper-tin alloy layer for 5 minutes.

[0148] [Arithmetic mean curvature of peak top point Spc]

[0149] Ten fields of view were observed using a laser microscope (VKX-1100 manufactured by KEYENCE CORPORATION, objective lens x 10), Spc was measured on the entire field of view image in accordance with ISO 25178, and the CV value (standard deviation / average) of Spc was calculated.

[0150] [Dynamic friction coefficient and stability]

[0151] A hemispherical female test piece having an inner diameter of 1.5 mm and a plate-shaped male test piece were produced for each sample in a manner simulating the contact portions of the male terminal and the female terminal of a mating connector. Using a friction measuring machine (horizontal load testing machine Model M-2152ENR) manufactured by Aiko Engineering Co., Ltd., the frictional force when the male test piece was pulled 10 mm in the horizontal direction at a sliding speed of 80 mm / minute was measured in a state where a load of 100 gf or more and 500 gf or less was applied between the female test piece and the male test piece, and the dynamic friction coefficient μ was calculated.

[0152] Regarding the dynamic friction coefficient, if the tin layer becomes thick, it is less affected by the underlying harder substrate, the nickel layer, and the copper-tin alloy layer, and the influence of the soft tin layer becomes greater, and thus the dynamic friction coefficient becomes higher. Test pieces in which the dynamic friction coefficient μ was 0.3 or less when the average thickness of the tin layer was less than 1.0 μm, the dynamic friction coefficient μ was 0.4 or less when the average thickness of the tin layer was 1.0 μm or more and less than 1.5 μm, and the dynamic friction coefficient μ was 0.45 or less when the average thickness of the tin layer was 1.5 μm or more were set as acceptable (A), and test pieces exceeding these values were set as unacceptable (B).

[0153] The average of the values measured 30 times by the above method was calculated, and test pieces in which the measured values of 30 times were within ±25% of the average were set as stability "A", and test pieces having measured values of ±25% or more were set as stability "B".

[0154] [Contact resistance value]

[0155] To evaluate the electrical reliability, the contact resistance was measured for each sample after heating at 150°C for 500 hours in the atmosphere. The measurement method followed JIS-C-5402, and the contact resistance was measured from 0 to 50 g of load variation by a 4-terminal contact resistance tester (YAMAZAKI SEIKISEISAKUSHO CO., LTD.: CRS-113-AU) in a sliding form (1 mm), and evaluated by the contact resistance value when the load was set to 50 g.

[0156] These results are shown in Tables 3, 4.

[0157] [Table 3]

[0158]

[0159] [Table 4]

[0160]

[0161] As is apparent from Tables 1 to 4, each of the examples shows that the dynamic friction coefficient μ decreases depending on the average thickness of the tin layer, and exhibits good stability of the dynamic friction coefficient μ. For example, in Example 8, although the tin layer thickness is slightly thick, 1.2 μm, it is not easily affected by the relatively hard underlying substrate, the nickel layer, the copper-tin alloy layer, but is easily affected by the soft tin layer, and the dynamic friction coefficient μ is 0.37, exhibiting good stability.

[0162] In contrast, in each of the comparative examples, the following adverse situations were confirmed. In Comparative Example 1, since the temperature in the furnace of the cooling furnace exceeds 70°C, the CV value of Spc is too large, and the stability of the dynamic friction coefficient μ is poor. In Comparative Example 2, since the cooling air amount of the primary cooling is too small, Spc is too small, the real contact area of the plated layers with each other becomes large, and thus the dynamic friction coefficient μ is poor, and the stability is poor. In Comparative Example 3, since the cooling air amount of the primary cooling is too large and Spc is too large, the penetration phenomenon occurs due to the unevenness of the surface at the time of the plug-in test, and thus the dynamic friction coefficient μ becomes too large, and the CV value of Spc is too large, and thus the stability of the dynamic friction coefficient μ is poor.

[0163] In Comparative Example 4, since the temperature in the furnace of the cooling furnace is less than 20°C, Spc, the CV value of Spc is too large, and the dynamic friction coefficient μ is too large, and the stability is poor. In Comparative Example 5, since the material reaching temperature is less than 150°C, the CV value of Spc is too large, and the stability of the dynamic friction coefficient μ is poor. In Comparative Example 6, since the material reaching temperature exceeds 220°C, the CV value of Spc is too large, and the stability of the dynamic friction coefficient μ is poor. In Comparative Example 7, since the cooling air amount of the primary cooling is too large, Spc, the CV value of Spc is too large, and the dynamic friction coefficient μ is too large, and the stability is poor.

[0164] In Comparative Example 8, the tin layer became thin because the tin plating layer was too thin, and the contact resistance value was poor. In Comparative Example 9, the tin layer became thick because the tin plating layer was too thick, and the dynamic friction coefficient was poor.

[0165] Industrial applicability

[0166] The present application can provide a film-coated copper terminal material that prevents adhesion when used as a connector, and that has a reduced dynamic friction coefficient and a stable dynamic friction coefficient, and that stably reduces the insertion and extraction force.

[0167] Explanation of symbols

[0168] 1 - film-coated copper terminal material; 2 - base material; 3 - tin layer; 4 - tin plating layer; 7 - plated material; 11 - film-coated copper terminal material; 12 - film; 13 - copper-tin alloy layer; 14 - tin layer; 15 - Cu3Sn alloy layer; 16 - Cu6Sn5 alloy layer; 17 - copper plating layer; 18 - tin plating layer; 19 - plated material; 21 - film-coated copper terminal material; 22 - film; 23 - nickel layer; 24 - tin layer; 25 - nickel plating layer; 26 - tin plating layer; 27 - plated material; 31 - film-coated copper terminal material; 32 - film; 33 - nickel layer; 34 - copper-tin alloy layer; 35 - tin layer; 36 - Cu3Sn alloy layer; 37 - Cu6Sn5 alloy layer; 41 - nickel plating layer; 42 - copper plating layer; 43 - tin plating layer; 44 - plated material.

Claims

1. A copper terminal material with a coating film, having a base material composed of copper or copper alloy and a coating film formed on the base material, characterized by, having a tin layer composed of tin or tin alloy with an average thickness of 0.2 μm or more and 2.0 μm or less on a surface of the coating film.

2. The copper terminal material with a coating film according to claim 1, characterized in that, the coating film has a copper-tin alloy layer composed of an alloy of copper and tin below the tin layer. The arithmetic mean curvature of the peak apex of the surface of the coating film is 10 mm -1 Above and 70 mm -1 Below, and the standard deviation / average of the arithmetic mean curvature of the peak apex when 10 fields of view are measured is 30% or less.

3. The copper terminal material with a coating film according to claim 1 or 2, characterized in that, the coating film has a nickel layer composed of nickel or nickel alloy in contact with the base material.

4. A method of manufacturing a copper terminal material with a coating film, which is a method of manufacturing a copper terminal material with a coating film having a coating film formed on a base material composed of copper or copper alloy, the method of manufacturing a copper terminal material with a coating film characterized by comprising: a plating step of forming a plated material on the base material, the plated material being formed by forming a plated layer having a tin plating layer composed of tin or tin alloy on a surface; and a reflow soldering step of heating the plated material to perform a reflow soldering process, the film thickness of the tin plating layer in the plating step being 0.2 μm or more and 3.0 μm or less, the reflow soldering process including: a heating step of heating the plated material to a peak temperature of 240°C or more and 300°C or less; a first cooling step of, after the heating step, passing the plated material through a cooling furnace having a furnace temperature of 20°C or more and 70°C or less to bring a material of the plated material to a temperature of 150°C or more and 220°C or less; and a second cooling step of, after the first cooling, cooling at a cooling rate of 100°C / sec or more and 300°C / sec or less.

5. The method of manufacturing a copper terminal material with a coating film according to claim 4, characterized in that, in the plating step, a copper plating layer composed of copper or copper alloy is formed below the tin plating layer.

6. The method of manufacturing a copper terminal material with a coating film according to claim 5, characterized in that, in the heating step, a temperature increase rate of the plated material is 20°C / sec or more and 75°C / sec or less.

7. The method of manufacturing a copper terminal material with a coating film according to claim 4, characterized in that, in the plating step, a nickel plating layer composed of nickel or nickel alloy is formed in contact with a surface of the base material.

8. The method of manufacturing a copper terminal material with a coating film according to claim 6, characterized in that, in the plating step, a nickel plating layer composed of nickel or nickel alloy is formed in contact with a surface of the base material.

9. The copper terminal material with a coating film according to claim 2, characterized in that, an average thickness of the copper-tin alloy layer is 0.2 μm or more and 2.5 μm or less.

10. The copper terminal material with a coating film according to claim 3, characterized in that, an average thickness of the nickel layer is 0.05 μm or more and 1.0 μm or less.

11. The copper terminal material with a coating film according to claim 1, characterized in that, ​ ​ ​ In the primary cooling step, cooling air is sprayed at a rate of 10 m 3 / minute or more and 300 m 3 / minute or less to the surface of the plated material. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The film has a copper-tin alloy layer and a nickel layer below the tin layer, the copper-tin alloy layer is composed of an alloy of copper and tin and has an average thickness of 0.2 μm or more and 2.5 μm or less, the nickel layer is in contact with the base material and is composed of nickel or a nickel alloy, and has an average thickness of 0.05 μm or more and 1.0 μm or less.

12. The method of producing a copper terminal material with a film according to claim 6, wherein The film thickness of the copper plating layer is 0.05 μm or more and 0.50 μm or less.

13. The method of producing a copper terminal material with a film according to claim 8, wherein The film thickness of the copper plating layer is 0.05 μm or more and 0.50 μm or less, and the film thickness of the nickel plating layer is 0.05 μm or more and 1.0 μm or less.

14. The method of producing a copper terminal material with a film according to claim 7, wherein The film thickness of the nickel plating layer is 0.05 μm or more and 1.0 μm or less.

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