Film coated copper terminal material and production method thereof

Abstract

To provide a film coated copper terminal material in which the insertion / extraction force is stably reduced by chiefly preventing adhesion from occurring when the material is used for a connector.SOLUTION: A base material made of copper or a copper alloy is coated with a film that is laminated with a nickel layer made of nickel or a nickel alloy, a copper-tin alloy layer, and a tin layer made of tin or a tin alloy in this order. The copper tin alloy layer includes a primary component of Cu6Sn5 alloy layer. The Cu6Sn5 alloy layer is an alloy layer having a compound in which a part of the copper is replaced by nickel, a part of the layer is exposed onto the surface of the tin layer and the exposure area ratio of the copper tin alloy layer exposed onto the surface of the tin layer is 1% or more and 60% or less. The tin layer has the average thickness of 0.2 μm or more and 1.2 μm or less. The nickel layer has the average thickness of 0.05 μm or more and 2.0 μm or less. The arithmetic average curvature Spc of peak points on the film surface is more than 70 mm-1 and 200 mm-1 or less, and the Spc standard deviation / average value is 30% or lower at the time of 10 visual field measurement.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a plated copper terminal material useful as a terminal for a connector used for connecting electrical wiring in automobiles, consumer devices, etc., particularly as a terminal for a multi-pin connector, and a method for producing the same. [Background technology]

[0002] Coated copper terminal materials include those that are made by forming a copper (Cu) plating layer and a tin (Sn) plating layer on a base material made of copper alloy, and then performing a reflow process to prevent the formation of whiskers, thereby forming a copper-tin (CuSn) alloy layer underneath the surface tin layer. These have high connection reliability and can be manufactured inexpensively, so they are widely used as terminal materials.

[0003] For example, Patent Document 1 discloses a conductive material in which a Cu-Sn alloy coating layer mainly composed of a Cu6Sn5 phase and a Sn coating layer are formed in this order on the surface of a base material made of a Cu alloy strip. This conductive material is produced by roughening the surface of the base material to a surface roughness of 0.15 μm or more in at least one direction and 4.0 μm or less in all directions, forming a Cu plating layer and a Sn plating layer in this order on the surface of the base material, and then performing a reflow treatment.

[0004] Patent Document 2 discloses a Sn-plated product in which a Cu-Sn alloy layer consisting of numerous Cu-Sn alloy crystal grains is formed on the surface of an underlayer on a substrate made of copper or a copper alloy, and an outermost layer consisting of a Sn layer in the recesses between adjacent Cu-Sn alloy crystal grains on the outermost surface. It also discloses that the area ratio of the Sn layer 16 on the outermost surface is 20 to 80%, and the maximum thickness of the Sn layer 16 is smaller than the average grain size of the Cu-Sn alloy crystal grains.

[0005] However, because the tin layer (Sn layer) is soft, adhesion between the contacts is likely to occur, and the increased contact area between the contacts results in excessive friction when inserting the connector, making insertion particularly difficult in multi-pin terminals.

[0006] Patent Document 3 discloses a plating material in which a base layer of Ni or the like is provided on a conductive substrate, an intermediate layer of copper or a copper alloy is provided on that, and an outermost layer made of a Cu-Sn intermetallic compound is provided on that. It states that because the outermost layer is made of a hard Cu-Sn intermetallic compound layer, fretting is unlikely to occur even if the contact pressure between terminals is reduced. However, when the outermost layer is a Cu-Sn intermetallic compound layer, copper (Cu) diffuses at high temperatures, making it easier for copper oxide to form on the surface. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-077307 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-180770 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-247060 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a plated copper terminal material that stably reduces insertion and removal force, mainly by preventing adhesion when used as a connector. [Means for solving the problem]

[0009] The plating film-coated copper terminal material of the present invention has a coating formed on a substrate made of copper or a copper alloy, in which a nickel layer made of nickel or a nickel alloy, a copper-tin alloy layer made of an alloy of copper and tin, and a tin layer made of tin or a tin alloy are laminated in this order, and the copper-tin alloy layer is mainly composed of a Cu6Sn5 alloy layer, and the Cu6Sn5 alloy layer is an alloy layer having a compound in which part of the copper is substituted with nickel, and a part is exposed on the surface of the tin layer, and the exposed area ratio of the copper-tin alloy layer exposed on the surface of the tin layer is 1% or more and 60% or less, the tin layer has an average thickness of 0.2 μm or more and 1.2 μm or less, and the nickel layer has an average thickness of 0.05 μm or more and 2.0 μm or less, and the arithmetic mean curvature Spc of the peaks on the surface of the coating is 70 mm ―1 Over 200mm ―1 or less, and the standard deviation / average value of the Spc when measuring 10 visual fields is within 30%.

[0010] This plated copper terminal material has a tin layer on the surface, which provides the excellent electrical properties inherent to the tin layer. If the average thickness of this tin layer is less than 0.2 μm, Cu diffuses at high temperatures, which can easily form Cu oxides on the surface, potentially increasing contact resistance. If it exceeds 1.2 μm, the soft tin layer increases the insertion and extraction force during use as a connector, making it difficult to reduce the insertion and extraction force required for connectors with multiple pins. The copper-tin alloy layer is mainly composed of a Cu6Sn5 alloy layer, and the Cu6Sn5 alloy layer contains a (Cu,Ni)6Sn5 alloy, a compound in which some of the copper is replaced with nickel, which allows the interface with the tin layer to have a sharp, uneven shape. In addition, the arithmetic mean curvature Spc of the peaks on the coating surface is 70 mm ―1 Over 200mm ―1 By setting the value to below 0.01, the dynamic friction coefficient can be reduced, and by setting the standard deviation / average value of Spc when measuring 10 fields of view to within 30%, the dynamic friction coefficient is stabilized and local fluctuations are suppressed.

[0011] The arithmetic mean curvature Spc of the peak is specified in ISO-25178, and the larger the value, the sharper the peak.―1 Below this, the surface becomes nearly flat, so the contact area when it comes into contact with the mating terminal as a connector becomes larger, and adhesion becomes more likely to occur, resulting in an increase in the coefficient of dynamic friction. ―1 If the standard deviation / average value of Spc exceeds 30%, the coefficient of dynamic friction will fluctuate locally and become unstable. Spc is 90mm ―1 More than 180mm ―1 It is more preferable that the standard deviation / average value of Spc is 25% or less.

[0012] In addition, the interface between the tin layer and the copper-tin alloy layer can be made into a sharply uneven shape, and the surface area has a structure in which the tin in the tin layer and the copper-tin alloy are combined, and the soft tin between the hard copper-tin alloy layers acts as a lubricant, reducing the coefficient of dynamic friction and improving wear resistance. In this case, if the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer is less than 1%, the effect of reducing the dynamic friction coefficient is poor, and if it exceeds 60%, the electrical connection characteristics may deteriorate. The lower limit of the area ratio is preferably 1.5% or more and the upper limit is 50% or less. More preferably, the lower limit is 2% or more and the upper limit is 40% or less.

[0013] The average thickness of the nickel layer is set to 0.05 μm or more and 2.0 μm or less because if it is less than 0.05 μm, the Ni content in the (Cu,Ni)6Sn5 alloy will be low, preventing the formation of a copper-tin alloy layer with a steeply uneven shape, while if it exceeds 2.0 μm, bending and other processes will become difficult. The average thickness of the nickel layer is preferably 0.075 μm or more, and more preferably 0.1 μm or more. Note that if the nickel layer is to function as a barrier layer to prevent Cu diffusion from the substrate and improve heat resistance, the thickness of the nickel plating layer is preferably 0.1 μm or more.

[0014] In the plated copper terminal material of the present invention, the Cu6Sn5 alloy layer preferably contains nickel in an amount of 0.1 at % or more and 25 at % or less.

[0015] The nickel content is set to 0.1 at% or more because, if it is less than 0.1 at%, an alloy layer having a compound in which part of the copper in the Cu6Sn5 alloy layer is replaced by nickel is not formed, and it is difficult to form a steep uneven shape, and the nickel content is set to 25 at% or less because, if it exceeds 25 at%, the shape of the copper-tin alloy layer tends to become too fine, and if the copper-tin alloy layer becomes too fine, it may not be possible to reduce the dynamic friction coefficient to 0.3 or less. The lower limit of the nickel content in the Cu6Sn5 alloy layer is desirably 2 at% or more, and the upper limit is preferably 20 at% or less.

[0016] In the plated copper terminal material of the present invention, the copper-tin alloy layer is preferably composed of a Cu3Sn alloy layer disposed on at least a portion of the nickel layer, and a Cu6Sn5 alloy layer disposed on at least either the Cu3Sn alloy layer or the nickel layer, and the volume ratio of the Cu3Sn alloy layer to the Cu6Sn5 alloy layer is preferably 20% or less.

[0017] Forming a Cu3Sn alloy layer on the nickel layer or at least a portion of the nickel layer and then forming a Cu6Sn5 alloy layer on them is advantageous for forming a steeply uneven surface on the copper-tin alloy layer. In this case, the volume ratio of the Cu3Sn alloy layer to the Cu6Sn5 alloy layer is set to 20% or less because if the volume ratio of the Cu3Sn alloy layer exceeds 20%, the Cu6Sn5 alloy layer does not grow vertically and the Cu6Sn5 alloy layer is unlikely to form a steeply uneven surface. The volume ratio of the Cu3Sn alloy layer to the Cu6Sn5 alloy layer is preferably 15% or less, more preferably 10% or less.

[0018] The method for producing a copper terminal material with a plating film of the present invention includes a plating step of forming a plated material by sequentially forming a nickel plating layer made of nickel or a nickel alloy, a copper plating layer made of copper or a copper alloy, and a tin plating layer made of tin or a tin alloy on the substrate, and a reflow step of heating the plated material to perform a reflow treatment, wherein the thickness of the nickel plating layer is 0.05 μm or more and 2.0 μm or less, the thickness of the copper plating layer is 0.05 μm or more and 0.40 μm or less, and the thickness of the tin plating layer is 0.5 μm or more and 1.5 μm or less, and the reflow step The method includes a primary heating step in which the plated material is heated to 240°C or higher at a temperature increase rate of 20°C / sec or higher and 75°C / sec or lower, a secondary heating step in which the plated material is heated at a temperature of 240°C or higher and 300°C or lower for 1 second or longer and 15 seconds or shorter after the primary heating step, a primary cooling step 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 reduce the material temperature to 150°C or higher and 220°C or lower after the primary cooling step, and a secondary cooling step in which the plated material is cooled at a cooling rate of 100°C / sec or higher and 300°C / sec or lower after the primary cooling step, and in the primary cooling step, cooling air is blown onto the surface of the plated material at a rate of 10 m / s. 3 / min more than 300m 3 The cross-sectional area of ​​the plated material threading part in the cooling furnace in the primary cooling process is 4m 2 Therefore, when converted into wind speed, the cooling air is blown at a speed of 2.5 m / min to 75 m / min.

[0019] As described above, by plating the substrate with nickel or a nickel alloy, a (Cu,Ni)6Sn5 alloy is formed after reflow treatment, which results in a sharp unevenness in the copper-tin alloy layer, making it possible to reduce the dynamic friction coefficient to 0.3 or less. If the thickness of the nickel plating layer is less than 0.05 μm, the nickel content in the (Cu,Ni)6Sn5 alloy will be low, preventing the formation of a copper-tin alloy with a sharply uneven shape. If the thickness exceeds 2.0 μm, bending and other processes will become difficult. If the nickel layer functions as a barrier layer to prevent copper diffusion from the substrate, improving heat resistance, or if wear resistance is to be improved, the thickness of the nickel plating layer is preferably 0.1 μm or more. The plating layer is not limited to pure nickel, but may also be a nickel alloy such as nickel-cobalt (Ni-Co) or nickel-tungsten (Ni-W).

[0020] If the thickness of the copper plating layer is less than 0.05 μm, the nickel content in the (Cu,Ni)6Sn5 alloy will be too high, the shape of the copper-tin alloy will be too fine, and it will not grow sufficiently in the vertical direction (the direction normal to the surface) to be exposed on the surface, making it impossible to achieve a dynamic friction coefficient of 0.3 or less.If the thickness exceeds 0.40 μm, the nickel content in the (Cu,Ni)6Sn5 alloy will be too low, and it will grow significantly in the horizontal direction (the direction perpendicular to the direction normal to the surface), preventing the formation of a copper-tin alloy layer with a steep, uneven shape. If the thickness of the tin plating layer is less than 0.5 μm, the tin layer will be thin after reflow, impairing the electrical connection characteristics. If the thickness exceeds 1.5 μm, the copper-tin alloy layer will be less exposed to the surface, making it difficult to achieve a dynamic friction coefficient of 0.3 or less.

[0021] The heating process is carried out under different conditions in two stages, which makes it easier to create solidified tin. In the first heating process, the material is rapidly heated to a high temperature of 240°C or higher at an early stage, and then the second heating is carried out at a temperature of 240°C to 300°C, which ensures a long time for the tin layer on the surface to melt.

[0022] This, combined with the exposure of a portion of the copper-tin alloy layer with a sharply asperity-like interface with the tin layer, causes the molten tin to aggregate and be repelled by the copper-tin alloy layer. In this case, if the heating rate in the primary heating is less than 20°C / s, copper atoms preferentially diffuse through the tin grain boundaries before the tin melts, resulting in abnormal growth of intermetallic compounds near the grain boundaries, making it difficult to form a copper-tin alloy layer with a sharply asperity-like shape. On the other hand, if the heating rate exceeds 75°C / s, the growth of the intermetallic compounds is insufficient, making it difficult to obtain the desired intermetallic compound layer during subsequent cooling. If the temperature reached in the primary heating step is less than 240°C, the tin melts insufficiently. In the secondary heating step, if the peak temperature exceeds 300°C, the copper-tin intermetallic compounds grow rapidly, resulting in excessively large asperities in the copper-tin alloy layer, which is undesirable. If the heating time exceeds 15 seconds, the tin aggregates excessively, tending to increase the coefficient of dynamic friction. If the heating time is less than 1 second, the tin will not be sufficiently melted, making it difficult to form a tin layer with the desired surface condition. The temperature rise rate in the secondary heating step is preferably 0°C / s or more and 19°C / s or less. That is, in the secondary heating step, the temperature may be raised or lowered as appropriate within the temperature range of 240°C or more and 300°C or less, or may be maintained at a constant temperature.

[0023] Next, in the cooling process, a primary cooling step is provided in which the plated material is passed through a cooling furnace with an internal temperature of 20°C to 70°C, and the material reaches a temperature of 150°C to 220°C, and is cooled to a temperature below the melting point of tin. Thereafter, in the secondary cooling step, the plated material is rapidly cooled at a high cooling rate. In this cooling step, a predetermined cooling air is blown onto the surface of the plated material in a cooling furnace with a predetermined internal temperature, thereby appropriately controlling the surface shape at a temperature below the melting point of tin, and the arithmetic mean curvature Spc of the peaks on the plated film surface is reduced to 70 mm. ―1 Over 200mm ―1 Below this, the standard deviation / average value (CV value) of Spc when measuring 10 visual fields can be kept within 30%.

[0024] In this case, if the temperature inside the cooling furnace is less than 20°C, the cooling rate will be too fast, and the Spc and CV values ​​(standard deviation / average value) of Spc will be too large. ―1Below this, the CV value (standard deviation / average value) of Spc cannot be kept within 30%. If it exceeds 70°C, the cooling time to a temperature below the melting point of tin is too long, resulting in an excessively large CV value (standard deviation / average value) of Spc. Regarding the material temperature of the plated material, if it is less than 150°C, the cooling time is too long, resulting in an excessively large CV value (standard deviation / average value) of Spc. If it exceeds 220°C, the tin is secondary cooled while still in a semi-molten state, resulting in an excessively large CV value (standard deviation / average value) of Spc. The material temperature is preferably 160°C or higher and 210°C or lower, and more preferably 170°C or higher and 200°C or lower. The cooling air volume is 10 m 3 If the cooling time is less than 70 mm / min, the cooling is insufficient and the Spc becomes too small. ―1 On the other hand, the cooling air volume cannot be increased to 300 m 3 If the time exceeds 1 / min, the molten tin will flow due to the large amount of air blown, and the Spc and CV values ​​(standard deviation / average value) of Spc will become excessively large.

[0025] The material is then rapidly cooled in a secondary cooling step to complete the growth of the intermetallic compound layer in the desired structure. If the cooling rate in this secondary cooling step is less than 100°C / sec, the intermetallic compound will progress too much, making it impossible to obtain the desired intermetallic compound shape. It is difficult to achieve a cooling rate of more than 300°C / sec. [Effects of the Invention]

[0026] According to the present invention, the arithmetic mean curvature Spc of the peaks on the surface of the tin layer is 70 mm ―1 Over 200mm ―1 or less, and the standard deviation / average value of Spc when measuring 10 visual fields is within 30%, which mainly prevents adhesion when used as a connector, thereby reducing and stabilizing the dynamic friction coefficient and enabling a stable reduction in insertion / extraction force. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a cross-sectional view schematically showing one embodiment of a plated copper terminal material of the present invention. [Figure 2] 2 is a cross-sectional view showing the plated material in the middle of manufacturing the plated layer-coated copper terminal material of FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] An embodiment of the plated copper terminal material of the present invention will be described. As shown in FIG. 1, the coated copper terminal material 1 of this embodiment has a coating 6 formed on a substrate 2 made of copper or a copper alloy, which is formed by laminating a nickel layer 3 made of nickel or a nickel alloy, a copper-tin alloy layer 4 made of an alloy of copper and tin, and a tin layer 5 made of tin or a tin alloy in this order.

[0029] The substrate 2 is a strip material formed in the shape of a strip plate, and its composition is not particularly limited as long as the surface is made of copper or a copper alloy.

[0030] As will be described later, the coating 6 on the substrate 2 is formed by sequentially plating the substrate 2 with nickel or a nickel alloy, copper or a copper alloy, and tin or a tin alloy, followed by heating and reflow treatment.

[0031] The average thickness of the nickel layer 3 is set to 0.05 μm or more and 2.0 μm or less because, if it is less than 0.05 μm, the Ni content in the (Cu,Ni)6Sn5 alloy is low, preventing the formation of a copper-tin alloy layer 4 with a sharply uneven shape, and if it exceeds 2.0 μm, bending and other processes become difficult. The average thickness of the nickel layer 3 is preferably 0.075 μm or more, and more preferably 0.1 μm or more. Note that, if the nickel layer 3 functions as a barrier layer to prevent Cu diffusion from the substrate 2 and improves heat resistance, the thickness of the nickel plating layer 12 is preferably 0.1 μm or more.

[0032] The copper-tin alloy layer 4 is formed to an average thickness of 0.2 μm or more and 2.5 μm or less. If the thickness is less than 0.2 μm, contact resistance may increase in high-temperature environments. If the thickness exceeds 2.5 μm, the copper-tin alloy layer 4 is too hard and may cause cracks during bending. The average crystal grain size of the copper-tin alloy layer 4 is preferably 0.2 μm or more and 1.5 μm or less.

[0033] The copper-tin alloy layer 4 is mainly composed of a Cu6Sn5 alloy layer 8, which is an alloy layer containing a compound in which part of the copper is substituted with nickel. In this case, it is preferable that the Cu6Sn5 alloy layer 8 contains nickel in an amount of 0.1 at % or more and 25 at % or less. If the nickel content in the Cu6Sn5 alloy layer 8 is less than 0.1 at%, a compound alloy layer in which part of the copper in Cu6Sn5 is replaced by nickel is not formed, and it is difficult to form a steep uneven shape. If the nickel content exceeds 25 at%, the shape of the copper-tin alloy layer 4 tends to become too fine, and if the copper-tin alloy layer 4 becomes too fine, it may be impossible to make the dynamic friction coefficient 0.3 or less. The lower limit of the nickel content in the Cu6Sn5 alloy layer 8 is preferably 2 at% or more, and the upper limit is 20 at% or less.

[0034] The copper-tin alloy layer 4 preferably comprises a Cu3Sn alloy layer 7 disposed on at least a portion of the nickel layer, and the Cu6Sn5 alloy layer 8 disposed on at least either the Cu3Sn alloy layer 7 or the nickel layer, and the volume ratio of the Cu3Sn alloy layer 7 to the Cu6Sn5 alloy layer 8 is preferably 20% or less. In this case, the volume ratio of the Cu3Sn alloy layer 7 to the Cu6Sn5 alloy layer 8 is preferably 20% or less.

[0035] Forming the Cu6Sn5 alloy layer 8 on the Cu3Sn alloy layer 7 is advantageous in forming a sharply uneven surface on the surface of the copper-tin alloy layer 4 (at the interface with the tin layer 5). In this case, if the volume ratio of the Cu3Sn alloy layer 7 to the Cu6Sn5 alloy layer 8 exceeds 20%, the Cu6Sn5 alloy layer 8 is unlikely to grow vertically, and the Cu6Sn5 alloy layer 8 is unlikely to form a sharply uneven surface. The volume ratio of the Cu3Sn alloy layer 7 to the Cu6Sn5 alloy layer 8 is preferably 15% or less, and more preferably 10% or less.

[0036] Furthermore, the exposed area ratio of the copper-tin alloy layer 4 exposed on the surface of the tin layer 5 is preferably 1% or more and 60% or less. If the exposed area ratio of the copper-tin alloy layer 4 on the surface of the tin layer 5 is less than 1%, the effect of reducing the dynamic friction coefficient is poor, and if it exceeds 60%, the electrical connection characteristics may deteriorate. The lower limit of the area ratio is preferably 1.5% or more and the upper limit is 50% or less. More preferably, the lower limit is 2% or more and the upper limit is 40% or less.

[0037] The average thickness of the tin layer 5 is 0.2 μm or more and 1.2 μm or less. The tin layer 5 has lubricity that reduces the insertion / extraction force of the connector and reduces contact resistance, resulting in excellent electrical properties. However, if the average thickness is less than 0.2 μm, it becomes difficult to obtain the excellent properties of tin. Furthermore, solderability and corrosion resistance may also be reduced. On the other hand, if the average thickness of the tin layer 5 exceeds 1.2 μm, the tin layer is soft and prone to adhesion, increasing the insertion / extraction force during use as a connector. This makes it difficult to reduce the insertion / extraction force associated with an increased number of pins in the connector. The average thickness of the tin layer 5 is preferably 0.3 μm or more and 1.1 μm or less.

[0038] As described above, a part of the copper-tin alloy layer 4 is exposed on the surface of the tin layer 5, and the arithmetic mean curvature Spc of the peaks is 70 mm over the entire surface of the tin layer 5 including the exposed part of the copper-tin alloy layer 4. ―1 Over 200mm ―1 or less, and the standard deviation / average value of Spc when measuring 10 visual fields is within 30%. The arithmetic mean curvature Spc of the peak is specified in ISO-25178, and the larger the value, the sharper the peak. ―1 Below this, the surface becomes nearly flat, so the contact area when it comes into contact with the mating terminal as a connector becomes larger, and adhesion becomes more likely to occur, resulting in an increase in the coefficient of dynamic friction. ―1 If the standard deviation / average value of Spc exceeds 30%, the coefficient of dynamic friction will fluctuate locally and become unstable. Spc is 90mm ―1 More than 180mm ―1 It is more preferable that the standard deviation / average value of Spc is 25% or less.

[0039] A method for manufacturing the film-coated copper terminal material 1 configured as above will be described. This coated copper terminal material 1 is formed by applying nickel plating made of nickel or a nickel alloy, copper plating made of copper or a copper alloy, and tin plating made of tin or a tin alloy to a substrate 2, thereby forming a plated material 11 in which a nickel plating layer 12, a copper plating layer 13, and a tin plating layer 14 are laminated in this order on the substrate 2, as shown in Figure 2, and then heating and performing a reflow treatment. As the substrate 2, a plate made of copper or a copper alloy is prepared, and the surface of this plate is cleaned by degreasing, pickling, or other treatments.

[0040] A common nickel plating bath may be used for nickel plating to form the nickel plating layer 12, such as a sulfuric acid bath containing sulfuric acid (H2SO4) and nickel sulfate (NiSO4) as the main components. The plating bath temperature is 20°C or higher and 60°C or lower, and the current density is 5 to 60 A / dm 2 The thickness of this nickel plating layer 12 is set to 0.05 μm or more and 2.0 μm or less. If it is less than 0.05 μm, the nickel content in the (Cu,Ni)6Sn5 alloy will be low, and a copper-tin alloy layer with a sharply uneven shape will not be formed, while if it exceeds 2.0 μm, bending and other processes will become difficult.

[0041] A common copper plating bath may be used for copper plating to form the copper plating layer 13, such as a copper sulfate bath containing copper sulfate (CuSO4) and sulfuric acid (H2SO4) as its main components. The plating bath temperature is 20 to 50°C, and the current density is 1 to 30 A / dm 2 The thickness of the copper plating layer 13 formed by this Cu plating is set to 0.05 μm or more and 0.40 μm or less. If the thickness is less than 0.05 μm, the Ni content in the (Cu,Ni)6Sn5 alloy becomes too high, and the shape of the copper-tin alloy becomes too fine, while if the thickness exceeds 0.40 μm, the Ni content in the (Cu,Ni)6Sn5 alloy becomes too low, and a copper-tin alloy layer with a sharply uneven shape cannot be formed.

[0042] A typical tin plating bath may be used as the plating bath for forming the tin plating layer 14, such as a sulfuric acid bath containing sulfuric acid (H2SO4) and stannous sulfate (SnSO4) as the main components. The plating bath temperature is 15 to 35°C, and the current density is 1 to 30 A / dm 2 The thickness of this tin plating layer 14 is set to 0.5 μm or more and 1.5 μm or less. If the thickness of the tin plating layer is less than 0.5 μm, the tin layer will be thin after reflow and the electrical connection characteristics will be impaired, while if the thickness exceeds 1.5 μm, the copper-tin alloy layer will be less exposed on the surface, making it difficult to achieve a dynamic friction coefficient of 0.3 or less.

[0043] The reflow treatment involves heating the plated material 11 to melt the copper plating layer 13 and the tin plating layer 14, followed by rapid cooling. Specifically, the treatment includes a primary heating step in which the plated material 11 is heated to 240°C at a heating rate of 20°C / sec to 75°C / sec in a heating furnace in a CO reducing atmosphere, a secondary heating step in which the plated material is heated at a temperature of 240°C to 300°C for 1 second to 15 seconds after the primary heating step, a primary cooling step in which the plated material is passed through a cooling furnace whose furnace temperature is 20°C to 70°C to reach a material temperature of 150°C to 220°C after the secondary heating step, and a secondary cooling step in which the plated material is cooled at a cooling rate of 100°C to 300°C / sec after the primary cooling. In this case, in the primary cooling step, cooling air is blown onto the surface of the plated material 11 at a speed of 10 m3 / min more than 300m 3 The temperature of the cooling air is preferably 30°C or higher and 60°C or lower.

[0044] By performing this reflow treatment in a reducing atmosphere, the formation of a tin oxide film with a high melting temperature on the surface of the tin plating layer 14 is prevented, and the reflow treatment can be performed at a lower temperature and in a shorter time, making it easier to produce the desired copper-tin alloy structure.

[0045] In addition, by carrying out the heating process in two stages under different conditions, it becomes easier to expose a portion of the copper-tin alloy layer 4 to the tin layer 5. In the first heating process, rapid heating is carried out to a high temperature of 240°C at an early stage, and then secondary heating is carried out at a temperature of 240°C or higher and 300°C or lower, thereby ensuring a long time for the tin layer 5 on the surface to melt.

[0046] This, combined with the exposure of a portion of the copper-tin alloy layer 4 with a sharply asperity-like interface with the tin layer 5, causes the molten tin to aggregate while being repelled by the copper-tin alloy layer 4. In this case, if the heating rate in the primary heating is less than 20°C / s, copper atoms preferentially diffuse through the tin grain boundaries before the tin melts, causing abnormal growth of intermetallic compounds near the grain boundaries, making it difficult to form a copper-tin alloy layer 4 with a sharply asperity-like shape. On the other hand, if the heating rate exceeds 75°C / s, the growth of the intermetallic compounds is insufficient, making it difficult to obtain the desired intermetallic compound layer in the subsequent cooling. If the temperature reached in this primary heating step is less than 240°C, the tin will not melt sufficiently.

[0047] In the secondary heating step, the temperature may be increased or decreased as needed or maintained at a specific temperature within the range of 240°C to 300°C. However, a peak temperature exceeding 300°C is undesirable because it rapidly grows copper-tin intermetallic compounds and results in excessive unevenness in the copper-tin alloy layer. A heating time of more than 15 seconds tends to result in excessive tin cohesion and a high coefficient of dynamic friction. A heating time of less than 1 second results in insufficient tin melting, making it difficult to form a tin layer 5 with the desired surface condition. The secondary heating time includes any time required for temperature increase or decrease from the temperature achieved in the primary heating step. The peak temperature of the secondary heating is preferably 250°C or higher. The heating rate of the secondary heating is preferably 0°C / s to 19°C / s.

[0048] The cooling process after heating is also divided into two stages, with a primary cooling step in which the plated material is passed through a cooling furnace with an internal temperature of 20°C to 70°C to reach a material temperature of 150°C to 220°C, where it is cooled to below the melting point of tin, and then rapidly cooled at a high cooling rate in the secondary cooling step. In this cooling step, a predetermined cooling air is blown onto the surface of the plated material 5 in a cooling furnace with a predetermined internal temperature, thereby appropriately controlling the surface shape at a temperature below the melting point of tin, and the arithmetic mean curvature Spc of the peaks on the surface of the coating (tin layer 5) is 70 mm. ―1 Over 200mm ―1 Below this, the standard deviation / average value (CV value) of Spc when measuring 10 visual fields can be kept within 30%.

[0049] In this case, if the temperature inside the cooling furnace is less than 20°C, the cooling rate will be too fast, and the Spc and CV values ​​(standard deviation / average value) of Spc will be too large. ―1Below this, the CV value (standard deviation / average value) of Spc cannot be kept within 30%. If it exceeds 70°C, the cooling time to a temperature below the melting point of tin is too long, resulting in an excessively large CV value (standard deviation / average value) of Spc. Regarding the material temperature of the plated material, if it is less than 150°C, the cooling time is too long, resulting in an excessively large CV value (standard deviation / average value) of Spc. If it exceeds 220°C, the tin is secondary cooled while still in a semi-molten state, resulting in an excessively large CV value (standard deviation / average value) of Spc. The material temperature is preferably 160°C or higher and 210°C or lower, and more preferably 170°C or higher and 200°C or lower. The cooling air volume is 10 m 3 If the cooling time is less than 70 mm / min, the cooling is insufficient and the Spc becomes too small. ―1 On the other hand, the cooling air volume cannot be increased to 300 m 3 If the time exceeds 1 / min, the molten tin will flow due to the large amount of air blown, and the Spc and CV values ​​(standard deviation / average value) of Spc will become excessively large. The cooling air is blown perpendicularly onto the plated material 11 from a height of about 10 cm above the surface of the plated material 11.

[0050] The material is then rapidly cooled in a secondary cooling process to achieve the desired surface shape. If the cooling rate in this secondary cooling process is less than 100°C / sec, the copper-tin intermetallic compound will grow, which is undesirable. It is difficult to achieve a cooling rate of more than 300°C / sec.

[0051] The coating of the plated copper terminal material 1 manufactured in this manner has the good electrical properties of the tin itself, since the surface is made of the tin layer 5. In addition, a part of the copper-tin alloy layer 4 is exposed on the surface of the tin layer 5, and the interface between the copper-tin alloy layer 4 and the tin layer 5 is formed in a steep uneven shape, so that the tin and copper-tin alloy of the tin layer 5 are combined near the surface, and the soft tin between the hard copper-tin alloy layers 4 acts as a lubricant, reducing the coefficient of dynamic friction and improving wear resistance.

[0052] The arithmetic mean curvature Spc of the peaks on the surface of the coating is 70 mm. ―1 Over 200mm ―1Since the standard deviation / average value of Spc when measuring 10 fields of view is within 30%, the dynamic friction coefficient is stabilized and local fluctuations are suppressed. Therefore, when used as a terminal material for a connector, the insertion and removal force can be stably reduced.

[0053] Furthermore, since the coating has the nickel layer 33 at the bottom, diffusion of copper from the substrate is prevented, thereby improving heat resistance. [Example]

[0054] A copper alloy plate having a thickness of 0.25 mm was used as the substrate, and nickel plating, copper plating, and tin plating were applied in this order under the following plating bath conditions. (nickel plating) Nickel sulfate: 300g / L Sulfuric acid: 2g / L Liquid temperature: 45℃ Current density: 20ASD (copper plating) Copper sulfate: 250g / L Sulfuric acid: 50g / L Liquid temperature: 25℃ Current density: 5ASD (tin plating) Tin sulfate: 75g / L Sulfuric acid: 85g / L Additive: 10g / L Liquid temperature: 25℃ Current density: 2ASD

[0055] Plated materials were prepared by forming each of these plating layers in order, and were subjected to reflow treatment under the conditions shown in Table 1.

[0056] [Table 1]

[0057] The stability of the obtained samples was evaluated by measuring the average thickness of the surface tin layer, the average thickness of the nickel layer, the nickel content in the Cu6Sn5 alloy layer, the volume ratio of the Cu3Sn alloy layer to the Cu6Sn5 alloy layer, the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer, the arithmetic mean bending of the peaks Spc, and the dynamic friction coefficient.

[0058] [Method for measuring the average thickness of each layer] The average thickness of the nickel layer and the average thickness of the tin layer were measured using an SII Nanotechnology Inc. fluorescent X-ray coating thickness meter (SEA5120A). To measure the thickness of the tin layer, the thickness of the entire tin-containing layer (including the copper-tin alloy layer and the tin layer, but the average thickness was calculated due to the unevenness of the tin precipitate) was first measured after reflow. Then, the sample was immersed for 5 minutes in an etching solution for stripping the copper-tin alloy film (a 10% aqueous solution of "Stripper L80" manufactured by Raybold Co., Ltd.) containing ingredients that do not corrode the copper-tin alloy layer, removing the tin layer and exposing the underlying copper-tin alloy layer. The thickness of the tin layer was then measured. The thickness of the tin layer was then defined as (the thickness of the entire tin-containing layer minus the thickness of the copper-tin alloy layer). To measure the thickness of the nickel layer, the sample was immersed for approximately 1 hour in an etching solution for stripping the nickel layer (a 10% aqueous solution of "Stripper L80" manufactured by Raybold Co., Ltd.) containing ingredients that do not corrode the nickel layer, removing the tin and copper-tin alloy layers, exposing the underlying nickel layer, and measuring the thickness of the nickel layer.

[0059] [Method for measuring nickel content in Cu6Sn5 alloy layer and presence or absence of Cu3Sn alloy layer] The nickel content in the Cu6Sn5 alloy layer and the presence or absence of the Cu3Sn alloy layer were determined by cross-sectional STEM image observation and area analysis using EDS analysis to identify the location of the alloy, the nickel content in the Cu6Sn5 alloy layer by point analysis, and the presence or absence of the Cu3Sn alloy layer by line analysis in the depth direction. In addition to cross-sectional observation, the presence or absence of the Cu3Sn alloy layer over a wider area was determined by immersing the sample in an etching solution for removing tin plating films (a 10% aqueous solution of "Stripper L80" manufactured by Raybold Co., Ltd.) for 5 minutes to remove the tin layer, exposing the underlying copper-tin alloy layer, and then measuring the X-ray diffraction pattern using CuKα radiation. The measurement conditions were as follows: PANalytical: MPD1880HR Tube used: Cu Kα ray Voltage: 45 kV Current: 40mA

[0060] [Method for measuring the exposed area ratio of the copper-tin alloy layer] The exposed area ratio of the copper-tin alloy layer was measured by removing the surface oxide film and then observing a 100 μm x 100 μm area with a scanning ion microscope. In terms of measurement principle, if the Cu6Sn5 alloy is present in the area approximately 20 nm deep from the outermost surface, it will appear white in the image. Therefore, using image processing software, the ratio of the area of ​​the white area to the total area of ​​the measurement area was regarded as the exposed area ratio of the copper-tin alloy layer.

[0061] [Method for measuring the volume ratio of Cu6Sn5 alloy layer and Cu3Sn alloy layer] The volume ratios of the Cu6Sn5 alloy layer and Cu3Sn alloy layer in the copper-tin alloy layer were determined by observing the cross section using a scanning ion microscope. For the measurement method, 50 lines were drawn vertically (depth direction) on each cross section of the three fields of view, and the lengths were measured at the locations of the Cu6Sn5 alloy layer and Cu3Sn alloy layer, and the height was calculated from the average value. Next, one horizontal line was drawn passing through the longest point of each Cu6Sn5 alloy layer and Cu3Sn alloy layer, and the width was measured. The area and area ratio could be calculated from the calculated height and width, and the volume ratio was calculated based on the assumption that the volume ratio ≒ area ratio.

[0062] [Method for measuring arithmetic mean peak curvature Spc] Ten fields of view were observed using a laser microscope (Keyence VKX-1100, objective lens ×10), and Spc was measured over the entire field of view in accordance with ISO 25178, and the CV value (standard deviation / average value) of Spc was calculated.

[0063] [Method for measuring the coefficient of dynamic friction and stability] To simulate the contact area between the male and female terminals of a mating connector, a hemispherical female test piece with an inner diameter of 1.5 mm and a plate-shaped male test piece were prepared for each sample. Using a friction tester (horizontal load tester, model M-2152ENR) manufactured by Aiko Engineering Co., Ltd., a load of 100 gf to 500 gf was applied between the female and male test pieces, and the male test piece was pulled horizontally for 10 mm at a sliding speed of 80 mm / min. The friction force was measured to determine the dynamic friction coefficient. A dynamic friction coefficient of 0.3 or less was considered pass (A), and anything above that was considered fail (B). The average value of 30 measurements was calculated using the above method, and those whose 30 measurements were within the range of the average value ±25% were rated stability "A", and those whose measurements were within ±25% or more were rated stability "B".

[0064] [Method for measuring contact resistance] To evaluate electrical reliability, the samples were heated in air at 150°C for 500 hours and the contact resistance was measured. The measurement method conformed to JIS-C-5402, and a four-terminal contact resistance tester (Yamazaki Seiki Kenkyusho: CRS-113-AU) was used to measure the contact resistance as a function of load (1 mm) from 0 to 50 g, and the contact resistance was evaluated as the contact resistance value when the load was set to 50 g.

[0065] These results are shown in Table 2.

[0066] [Table 2]

[0067] From these results, it can be seen that the examples were excellent in both the dynamic friction coefficient and its stability, and the contact resistance.

[0068] In contrast, in Comparative Example 1, the primary cooling airflow was too strong, resulting in excessively large Spc and Spc CV values, and the dynamic friction coefficient was high and its stability was poor. In Comparative Example 2, the furnace temperature during primary cooling was too low, resulting in excessively large Spc and Spc CV values, and the dynamic friction coefficient was high and its stability was poor. In Comparative Example 3, the copper plating layer was too thick, resulting in an excessively large exposed area ratio of the copper-tin alloy layer, and the contact resistance exceeded 10 mΩ. In Comparative Example 4, the average thickness of the tin layer was too thin, resulting in an excessively large exposed area ratio of the copper-tin alloy layer, and the contact resistance exceeded 10 mΩ.

[0069] In Comparative Example 5, the average thickness of the nickel layer was too thin, resulting in a small exposed area ratio of the copper-tin alloy layer and a high dynamic friction coefficient. In Comparative Example 6, the furnace temperature during primary cooling was too high, resulting in an excessively large CV value of Spc, and the stability of the dynamic friction coefficient was poor. In Comparative Example 7, the copper plating layer was too thin, and the heating rate during the primary heating step was too high and the primary heating temperature was too low, resulting in insufficient tin melting. This resulted in an excessively small exposed area ratio of the copper-tin alloy layer, a high dynamic friction coefficient, and poor stability. In Comparative Example 8, the primary cooling air volume was too weak, resulting in an excessively small Spc, a large true contact area, and increased adhesion, resulting in a high dynamic friction coefficient. In Comparative Example 9, the tin plating layer was too thick, resulting in a small exposed area ratio of the copper-tin alloy layer and a high dynamic friction coefficient. In addition, the primary cooling temperature was too low, resulting in an excessively large CV value of Spc, and the stability of the dynamic friction coefficient was poor. In Comparative Example 10, the primary cooling temperature reached was too high, resulting in an excessively large CV value of Spc, and the stability of the dynamic friction coefficient was poor. [Explanation of symbols]

[0070] 1 Coated copper terminal material 2 Base material 3 Nickel layer 4 Copper-tin alloy layer 5 tin layer 6. Coating 7 Cu3Sn alloy layer 8 Cu6Sn5 alloy layer 11 Plating materials 12 Nickel plating layer 13 Copper plating layer 14 Tin plating layer

Claims

[Request 1] A coating is formed on a substrate made of copper or a copper alloy, in which a nickel layer made of nickel or a nickel alloy, a copper-tin alloy layer made of an alloy of copper and tin, and a tin layer made of tin or a tin alloy are laminated in this order, and the copper-tin alloy layer is ６ Sn ５ The alloy layer is mainly composed of Cu ６ Sn ５ The alloy layer is an alloy layer having a compound in which part of the copper is substituted with nickel, and a part of the alloy layer is exposed on the surface of the tin layer, and the exposed area ratio of the copper-tin alloy layer exposed on the surface of the tin layer is 1% or more and 60% or less, the tin layer has an average thickness of 0.2 μm or more and 1.2 μm or less, the nickel layer has an average thickness of 0.05 μm or more and 2.0 μm or less, and the arithmetic mean curvature Spc of the peaks on the surface of the coating is 70 mm ―１ Over 200mm ―１ and wherein the standard deviation / average value of the Spc when measuring 10 visual fields is within 30%. Request 2 The Cu ６ Sn ５ 2. The plated copper terminal material according to claim 1, wherein the alloy layer contains nickel in an amount of 0.1 at % or more and 25 at % or less. Request 3 The copper-tin alloy layer is a Cu layer disposed on at least a portion of the nickel layer. ３ Sn alloy layer and the Cu ３ The Cu layer disposed on at least one of the Sn alloy layer and the nickel layer. ６ Sn ５ and an alloy layer, ６ Sn ５ Cu for alloy layer ３ 3. The plated copper terminal material according to claim 1, wherein the volume ratio of the Sn alloy layer is 20% or less. Request 4 A method for manufacturing a copper terminal material with a plating film, in which a film is formed on a substrate made of copper or a copper alloy, includes a plating step of forming a plated material on the substrate by sequentially forming a nickel plating layer made of nickel or a nickel alloy, a copper plating layer made of copper or a copper alloy, and a tin plating layer made of tin or a tin alloy, and a reflow step of heating the plated material to perform a reflow treatment, in which the thickness of the nickel plating layer is 0.05 μm or more and 2.0 μm or less, the thickness of the copper plating layer is 0.05 μm or more and 0.40 μm or less, and the thickness of the tin plating layer is 0.5 μm or more and 1.5 μm or less. The reflow process includes a primary heating step of heating the plated material to 240°C or higher at a temperature increase rate of 20°C / sec or higher and 75°C / sec or lower, a secondary heating step of heating the plated material at a temperature of 240°C or higher and 300°C or lower for 1 second or higher and 15 seconds or lower after the primary heating step, a primary cooling step of passing the plated material through a cooling furnace having an internal temperature of 20°C or higher and 70°C or lower to reduce the material temperature to 150°C or higher and 220°C or lower after the primary cooling, and a secondary cooling step of cooling the plated material at a cooling rate of 100°C / sec or higher and 300°C / sec or lower after the primary cooling step, and in the primary cooling step, cooling air is blown onto the surface of the plated material at a rate of 10 m / s. ３ / min or more 300m ３ 1. A method for producing a plated copper terminal material, comprising: blowing air at a rate of 1 / min or less.

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