Copper terminal material with plating film and method for manufacturing same

Abstract

In the present invention, a coating film is formed on a substrate made of copper or a copper-tin alloy, the coating film being a laminate in which 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 are layered in this order. The copper-tin alloy layer is composed mainly of a Cu6Sn5 alloy layer. The Cu6Sn5 alloy layer is an ally layer having a compound in which a part of the copper is substituted with nickel, and a part of the alloy layer is exposed on the surface of the tin layer. The exposed area ratio of the copper-tin alloy layer exposed on the surface of the tin layer is 1-60%. The tin layer has an average thickness of 0.20-1.20 μm, and the nickel layer has an average thickness of 0.05-2.00 μm. The arithmetic average curve Spc of the crest point on the surface of the coating film exceeds 70 mm-1 but does not exceed 200 mm-1, and the standard deviation / average value of Spc found when visual field measurement is performed 10 times is 30% or less.

Description

Plated copper terminal material and its manufacturing method

[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.

[0002] This application claims priority based on Japanese Patent Application No. 2024-046299, filed on March 22, 2024, the contents of which are incorporated herein by reference.

[0003] Coated copper terminal materials include those that are made by forming a copper (Cu) plating layer and a tin (Sn) plating layer on a substrate made of a copper alloy, and then performing a reflow process to suppress the generation of whiskers, thereby forming a copper-tin (CuSn) alloy layer below the surface tin layer. These have high connection reliability and can be manufactured inexpensively, so they are widely used as terminal materials.

[0004] For example, in Patent Document 1, a Cu alloy plate is formed on the surface of a base material. ６ Sn ５ The document discloses a conductive material having a Cu—Sn alloy coating layer mainly composed of a Cu—Sn alloy phase and a Sn coating layer formed in this order. This conductive material is produced by roughening the surface of a 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.

[0005] Furthermore, 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 recesses between adjacent Cu-Sn alloy crystal grains on the outermost surface, and it is described 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.

[0006] 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.

[0007] 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 thereon, and an outermost layer made of a Cu-Sn intermetallic compound is provided thereon. It describes 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.

[0008] However, if the outermost layer is a Cu--Sn intermetallic compound layer, copper (Cu) diffuses at high temperatures, and copper oxides are likely to form on the surface.

[0009] JP 2006-077307 A JP 2015-180770 A JP 2007-247060 A

[0010] 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.

[0011] The plating film-coated copper terminal material of the present invention is a coating formed by laminating 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 on a substrate made of copper or a copper alloy 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 0.20 μm or more and 1.20 μm or less, the nickel layer has an average thickness of 0.05 μm or more and 2.00 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%.

[0012] 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 0.20 μm, Cu diffuses at high temperatures, which can easily form Cu oxides on the surface, resulting in increased contact resistance. If the average thickness of the tin layer is more than 1.20 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.

[0013] The copper-tin alloy layer is Cu ６ Sn ５ The alloy layer is the main component, and Cu ６ Sn ５ The alloy layer is a compound in which part of the copper is replaced by nickel (Cu, Ni). ６ Sn ５ The presence of the alloy allows the interface with the tin layer to have a sharply uneven shape.

[0014] 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 be less than or equal to 10, the dynamic friction coefficient can be reduced, and by setting the standard deviation / average value of Spc when measuring 10 visual fields to be within 30%, the dynamic friction coefficient is stabilized and local fluctuations are also suppressed.

[0015] 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 tends 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. --１ 180mm or more --１It is more preferable that the standard deviation / average value of Spc is 25% or less.

[0016] In addition, the interface between the tin layer and the copper-tin alloy layer can be made into a steep uneven shape, and the tin of the tin layer and the copper-tin alloy are combined near the surface, and the soft tin between the hard copper-tin alloy layers acts as a lubricant, reducing the dynamic friction coefficient 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 be reduced.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.

[0017] The reason why the average thickness of the nickel layer is set to 0.05 μm or more and 2.00 μm or less is that if it is less than 0.05 μm, (Cu, Ni) ６ Sn ５ Since the Ni content in the alloy is low, a copper-tin alloy layer with a steep uneven shape is not formed, and if the thickness exceeds 2.00 μm, bending and other processes become difficult. The average thickness of the nickel layer is desirably 0.075 μm or more, more desirably 0.10 μm or more. Note that, when 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 desirably 0.10 μm or more.

[0018] The plating film-coated copper terminal material of the present invention is ６ Sn ５ The alloy layer preferably contains nickel in an amount of 0.1 at % or more and 25 at % or less.

[0019] The nickel content is specified to be 0.1 at% or more because if it is less than 0.1 at%, Cu ６ Sn ５ This is because it is difficult to form an alloy layer having a compound in which part of the copper in the alloy layer is replaced by nickel, and it is difficult to form a sharp uneven shape, and the reason why it is specified to be 25 at% or less is that 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 make the dynamic friction coefficient 0.3 or less. ６ Sn ５The lower limit of the nickel content in the alloy layer is desirably 2 at % or more, and the upper limit is preferably 20 at % or less.

[0020] In the plating film-coated copper terminal material of the present invention, the copper-tin alloy layer is a Cu layer disposed on at least a part of the nickel layer. ３ The Sn alloy layer and the Cu layer on the nickel layer ３ On the Sn alloy layer, and ３ The Cu layer is formed so as to extend over the nickel layer where no Sn alloy layer is present. ６ Sn ５ and an alloy layer, ６ Sn ５ Cu for alloy layer ３ The volume ratio of the Sn alloy layer is preferably 20% or less.

[0021] A nickel layer or at least a part of the layer is Cu ３ Sn alloy layers are formed, and Cu is deposited on them. ６ Sn ５ The formation of the alloy layer is advantageous in forming a sharply uneven surface on the copper-tin alloy layer. ６ Sn ５ Cu for alloy layer ３ The volume ratio of the Sn alloy layer is set to 20% or less because Cu ３ When the volume ratio of the Sn alloy layer exceeds 20%, Cu ６ Sn ５ The alloy layer does not grow in the thickness direction, and Cu ６ Sn ５ This is because the alloy layer is less likely to have a steep uneven shape. ６ Sn ５ Cu for alloy layer ３ The volume ratio of the Sn alloy layer is preferably 15% or less, and more preferably 10% or less.

[0022] 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 2.00 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 0.50 μm or more and 1.50 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, wherein 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 The cross-sectional area of ​​the plated material passing through the cooling furnace in the primary cooling process is, for example, 4 m 2 In this case, the cooling air is blown at a speed of 2.5 m / min or more and 75 m / min or less when converted into wind speed.

[0023] As described above, by plating the substrate with nickel or nickel alloy, after reflow treatment (Cu, Ni) ６ Sn ５ This allows the copper-tin alloy layer to have sharp irregularities, making it possible to reduce the coefficient of dynamic friction to 0.3 or less.

[0024] When the thickness of the nickel plating layer is less than 0.05 μm, (Cu, Ni) ６ Sn ５The nickel content in the alloy decreases, making it difficult to form a copper-tin alloy with a sharply uneven shape, and if the thickness exceeds 2.00 μm, bending and other processes become difficult. When the nickel layer functions as a barrier layer to prevent copper diffusion from the substrate and improves heat resistance, or when wear resistance is improved, the thickness of the nickel plating layer is desirably 0.10 μm or more. The plating layer is not limited to pure nickel, and may be a nickel alloy such as nickel-cobalt (Ni—Co) or nickel-tungsten (Ni—W).

[0025] When the thickness of the copper plating layer is less than 0.05 μm, (Cu, Ni) ６ Sn ５ The nickel content in the alloy increases, and the shape of the copper-tin alloy becomes too fine, and the copper-tin alloy does not grow sufficiently in the thickness direction (surface normal direction) to be exposed on the surface, so the dynamic friction coefficient cannot be made 0.3 or less. If the nickel content exceeds 0.40 μm, the (Cu, Ni) ６ Sn ５ The nickel content in the alloy decreases, causing the copper-tin alloy layer to grow larger in the lateral direction (the direction perpendicular to the surface normal direction), and preventing the formation of a steeply uneven copper-tin alloy layer.

[0026] If the thickness of the tin plating layer is less than 0.50 μm, the tin layer will be thin after reflow, impairing the electrical connection characteristics, and if it exceeds 1.50 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.

[0027] The heating process is performed under different conditions in two stages, which facilitates the formation of solidified tin portions on the surface. In the first heating process, rapid heating is performed to a high temperature of 240°C or higher at an early stage, and then secondary heating is performed at a temperature of 240°C or higher but not higher than 300°C, ensuring a long melting time for the tin layer on the surface. This, combined with the exposure of part of the copper-tin alloy layer, which has a sharp, uneven interface with the tin layer, on the surface, causes the molten tin to aggregate as if repelled by the copper-tin alloy layer, and then in the cooling process, island-like solidified tin portions protruding from the surface of the tin layer are formed.

[0028] 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 with a steeply uneven 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 the primary heating step is less than 240°C, the tin melting is insufficient. In the secondary heating step, if the peak temperature exceeds 300°C, the copper-tin intermetallic compounds grow rapidly, resulting in excessive unevenness in the copper-tin alloy layer, which is undesirable. If the heating time exceeds 15 seconds, the tin aggregation tends to become excessive, resulting in an increased dynamic friction coefficient. If the heating time is less than 1 second, the tin melting is insufficient, making it difficult to form a tin layer with the desired surface condition. The heating 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 increased or decreased as appropriate within the temperature range of 240° C. or more and 300° C. or less, or may be maintained at a constant temperature.

[0029] Next, in the cooling process, a primary cooling step is provided in which the plated material is passed through a cooling furnace having 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, and then 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 having 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 In the following, the standard deviation / average value (CV value) of Spc when measuring 10 visual fields can be kept within 30%.

[0030] In this case, if the temperature inside the cooling furnace is less than 20°C, the cooling rate is too fast and the Spc and CV values ​​(standard deviation / average value) of Spc become excessively large. --１Below this, the CV value (standard deviation / average value) of Spc cannot be kept within 30%. If the temperature 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, more preferably 170°C or higher and 200°C or lower. The cooling air volume is 10 m ３ If the cooling rate is less than 70 mm / min, the cooling rate will not be sufficient and the Spc will be 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.

[0031] The alloy 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 exceeding 300°C / sec.

[0032] 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%, thereby preventing the occurrence of adhesion when used as a connector, thereby reducing and stabilizing the dynamic friction coefficient, and enabling a stable reduction in insertion / extraction force.

[0033] 1 is a cross-sectional view showing a plated material during the manufacturing process of the plated copper terminal material of FIG. 1.

[0034] An embodiment of the plated copper terminal material of the present invention will be described.

[0035] 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.

[0036] The substrate 2 is a strip material formed in a strip shape, and its composition is not particularly limited as long as the surface is made of copper or a copper alloy.

[0037] 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.

[0038] The reason why the average thickness of the nickel layer 3 is set to 0.05 μm or more and 2.00 μm or less is that if it is less than 0.05 μm, the (Cu, Ni) ６ Sn ５ The Ni content in the alloy decreases, and the copper-tin alloy layer 4 does not have a sharply uneven shape. If the thickness exceeds 2.00 μm, bending and other processes become difficult. The average thickness of the nickel layer 3 is desirably 0.075 μm or more, and more desirably 0.10 μm or more. Note that, when the nickel layer 3 is to function as a barrier layer to prevent Cu diffusion from the substrate 2 and improve heat resistance, the thickness of the nickel plating layer 12 is desirably 0.10 μm or more.

[0039] The copper-tin alloy layer 4 is formed to an average thickness of 0.20 μm or more and 2.50 μm or less. If the thickness is less than 0.20 μm, contact resistance may increase in a high-temperature environment. If the thickness exceeds 2.50 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 0.20 μm or more and 1.50 μm or less.

[0040] The copper-tin alloy layer 4 is made of Cu ６ Sn ５ The alloy layer 8 is mainly composed of Cu ６ Sn ５ The alloy layer 8 is an alloy layer containing a compound in which part of the copper is replaced by nickel.

[0041] In this case, Cu ６ Sn ５ The alloy layer 8 preferably contains nickel in an amount of 0.1 at % or more and 25 at % or less.

[0042] Cu ６ Sn ５ When the nickel content in the alloy layer 8 is less than 0.1 at %, Cu ６ Sn ５ If the content of Cu 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. ６ Sn ５ The lower limit of the nickel content in the alloy layer 8 is preferably 2 at % or more, and the upper limit is preferably 20 at % or less.

[0043] The copper-tin alloy layer 4 is a Cu layer disposed on at least a portion of the nickel layer. ３ Sn alloy layer 7 and Cu on the nickel layer ３ On the Sn alloy layer, and Cu ３ A Cu layer formed on a nickel layer where no Sn alloy layer is present ６ Sn ５ The alloy layer 8 is made of Cu. ６ Sn ５ Cu for alloy layer 8 ３ The volume ratio of the Sn alloy layer 7 is preferably 20% or less. ６ Sn ５ Cu for alloy layer 8 ３ The volume ratio of the Sn alloy layer 7 is preferably 20% or less.

[0044] This Cu ３ Cu is deposited on the Sn alloy layer 7. ６ Sn ５ The formation of the alloy layer 8 is advantageous in forming a sharply uneven surface on the surface of the copper-tin alloy layer 4 (the interface with the tin layer 5). ６ Sn ５ Cu for alloy layer 8 ３ When the volume ratio of the Sn alloy layer 7 exceeds 20%, Cu ６ Sn５ The alloy layer 8 is difficult to grow in the thickness direction, and Cu ６ Sn ５ The alloy layer 8 is unlikely to have a steep uneven shape. ６ Sn ５ Cu for alloy layer 8 ３ The volume ratio of the Sn alloy layer 7 is preferably 15% or less, and more preferably 10% or less.

[0045] 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%, there is a risk of deterioration in electrical connection characteristics. 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.

[0046] The average thickness of the tin layer 5 is 0.20 μm or more and 1.20 μm or less. The tin layer 5, due to its lubricity, keeps the insertion / extraction force of the connector low and reduces contact resistance, resulting in excellent electrical properties. However, if the average thickness is less than 0.20 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 1.20 μm, the tin layer is soft and therefore prone to adhesion, increasing the insertion / extraction force during use as a connector, making it difficult to reduce the insertion / extraction force associated with an increased number of pins in the connector. The average thickness of this tin layer 5 is preferably 0.30 μm or more and 1.10 μm or less.

[0047] 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%.

[0048] The arithmetic mean curvature Spc of the peak is specified in ISO-25178, and the larger the value, the sharper the peak. --１Below 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 tends 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. --１ 180mm or more --１ It is more preferable that the standard deviation / average value of Spc is 25% or less.

[0049] The following describes a method for manufacturing the film-coated copper terminal material 1 configured as described above. This film-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 Fig. 2, and then heating and performing a reflow treatment.

[0050] 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.

[0051] The nickel plating for forming the nickel plating layer 12 may be carried out using a general nickel plating bath, for example, sulfuric acid (H ２ SO ４ ) and nickel sulfate (NiSO ４ The temperature of the plating bath is 20°C or higher and 60°C or lower, and the current density is 5 to 60 A / dm ２ The thickness of the nickel plating layer 12 is set to 0.05 μm or more and 2.00 μm or less. If it is less than 0.05 μm, the (Cu, Ni) ６ Sn ５ This is because the nickel content in the alloy becomes small, making it impossible to form a copper-tin alloy layer with a sharply uneven shape, and if the thickness exceeds 2.00 μm, bending and other processes become difficult.

[0052] Copper plating for forming the copper plating layer 13 can be performed using a general copper plating bath, for example, copper sulfate (CuSO ４ ) and sulfuric acid (H ２ SO ４ 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 it is less than 0.05 μm, (Cu, Ni) ６ Sn ５ When the Ni content in the alloy becomes large and the shape of the copper-tin alloy becomes too fine, exceeding 0.40 μm, (Cu, Ni) ６ Sn ５ This is because the nickel content in the alloy is reduced, and a copper-tin alloy layer with a sharply uneven shape is not formed.

[0053] As the plating bath for tin plating to form the tin plating layer 14, a general tin plating bath may be used, for example, sulfuric acid (H ２ SO ４ ) and stannous sulfate (SnSO ４ 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 0.50 μm or more and 1.50 μm or less. If the thickness of the tin plating layer is less than 0.50 μm, the tin layer becomes thin after reflow, impairing the electrical connection characteristics, while if the thickness exceeds 1.50 μm, the copper-tin alloy layer is exposed less on the surface, making it difficult to achieve a dynamic friction coefficient of 0.3 or less.

[0054] 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 temperature increase 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 reduce the material temperature to 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.

[0055] 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 m ３ / min or more 300m ３ The temperature of the cooling air is preferably 30°C or higher and 60°C or lower.

[0056] By performing this reflow treatment in a reducing atmosphere, it is possible to prevent the formation of a tin oxide film with a high melting temperature on the surface of the tin plating layer 14, and it is possible to perform the reflow treatment at a lower temperature in a shorter time, making it easier to produce the desired copper-tin alloy structure.

[0057] Furthermore, by carrying out the heating process in two stages under different conditions, it is possible to easily 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 melting the surface tin layer 5.

[0058] This, combined with the exposure of a portion of the copper-tin alloy layer 4 with a sharply uneven 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 / sec, 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 uneven shape. On the other hand, if the heating rate exceeds 75°C / sec, the growth of the intermetallic compounds becomes insufficient, making it difficult to obtain a 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.

[0059] 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 the copper-tin intermetallic compound rapidly grows, resulting 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 dynamic friction coefficient. 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 more preferably 250°C or higher. The heating rate of the secondary heating is preferably 0°C / s to 19°C / s.

[0060] 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, whereby the material 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 In the following, the standard deviation / average value (CV value) of Spc when measuring 10 visual fields can be kept within 30%.

[0061] In this case, if the temperature inside the cooling furnace is less than 20°C, the cooling rate is too fast and the Spc and CV values ​​(standard deviation / average value) of Spc become excessively large. -１ Below this, the CV value (standard deviation / average value) of Spc cannot be kept within 30%. If the temperature 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, more preferably 170°C or higher and 200°C or lower. The cooling air volume is 10 m ３ If the cooling rate is less than 70 mm / min, the cooling rate will not be sufficient and the Spc will be 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.

[0062] 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 .

[0063] The material is then rapidly cooled in a secondary cooling step to achieve the desired surface shape. If the cooling rate in this secondary cooling step is less than 100°C / sec, copper-tin intermetallic compounds will grow, which is undesirable. It is difficult to achieve a cooling rate of more than 300°C / sec.

[0064] 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.

[0065] The arithmetic mean curvature Spc of the peaks on the surface of the coating is 70 mm -１ Over 200mm -１ Since 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.

[0066] Therefore, when used as a terminal material for a connector, the insertion and removal force can be stably reduced.

[0067] Furthermore, since the coating has the nickel layer 33 at the bottom, diffusion of copper from the substrate is prevented, thereby improving heat resistance.

[0068] A copper alloy plate having a thickness of 0.25 mm was used as a substrate, and nickel plating, copper plating, and tin plating were applied in this order under the following plating bath conditions.

[0069] (Nickel plating) Nickel sulfate: 300 g / L Sulfuric acid: 2 g / L Solution temperature: 45°C Current density: 20 ASD

[0070] (Copper plating) Copper sulfate: 250g / L Sulfuric acid: 50g / L Liquid temperature: 25℃ Current density: 5ASD

[0071] (Tin plating) Tin sulfate: 75 g / L Sulfuric acid: 85 g / L Additive: 10 g / L Solution temperature: 25°C Current density: 2ASD

[0072] Plated materials were prepared by forming each of these plating layers in order, and were subjected to a reflow treatment under the conditions shown in Table 1.

[0073]

[0074] The average thickness of the tin layer on the surface of the obtained sample, the average thickness of the nickel layer, and the Cu ６ Sn ５ Nickel content in the alloy layer, Cu ６ Sn ５ The volume ratio of the Cu3Sn alloy layer to the alloy layer, the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer, the arithmetic mean curve of the peaks Spc, and the dynamic friction coefficient were measured to evaluate the stability.

[0075] [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 a fluorescent X-ray film thickness meter (SEA5120A) manufactured by SII Nanotechnology Inc. To measure the thickness of the tin layer, first, the thickness of the entire tin-containing layer of the sample after reflow (this thickness includes the copper-tin alloy layer portion and the tin layer portion, but since the solidified tin portion has unevenness, it is calculated as the average thickness) was measured, and then the tin layer was removed by immersing the sample for 5 minutes in an etching solution for stripping a plating film (a 10% aqueous solution of "Stripper L80" manufactured by Leybold Co., Ltd.) containing components that do not corrode the copper-tin alloy layer, exposing the copper-tin alloy layer underneath and measuring the thickness of the copper-tin alloy layer. The thickness of the tin layer was then defined as (the thickness of the entire tin-containing layer - the thickness of the copper-tin alloy layer). To measure the thickness of the nickel layer, the tin layer and copper-tin alloy layer were removed by immersing the specimen for about 1 hour in an etching solution for stripping the plated film (a stock solution of "Stripper L80" manufactured by Leybold Co., Ltd.) which was made of components that did not corrode the nickel layer, thereby exposing the underlying nickel layer, and the thickness of the nickel layer was measured.

[0076] [Cu ６ Sn ５ Nickel content in the alloy layer, Cu ３ Method for determining the presence or absence of an Sn alloy layer] Cu ６ Sn ５ Nickel content in the alloy layer, Cu ３ The presence or absence of the Sn alloy layer was determined by identifying the location of the alloy through cross-sectional STEM image observation and surface analysis using EDS analysis, and by point analysis, the Cu ６ Sn ５ The nickel content in the alloy layer was determined by line analysis in the depth direction. ３ The presence or absence of a Sn alloy layer was examined. In addition to cross-sectional observation, the presence or absence of a Cu alloy layer was also examined over a wider area. ３ The presence or absence of the Sn alloy layer was determined by immersing the specimen for 5 minutes in an etching solution for stripping tin plating films (a 10% aqueous solution of "Stripper L80" manufactured by Leybold Co., Ltd.) to remove the tin layer and expose 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: CuKα radiation, voltage: 45 kV, current: 40 mA.

[0077] [Method for measuring the exposed area ratio of the copper-tin alloy layer] After removing the surface oxide film, the exposed area ratio of the copper-tin alloy layer was measured by observing a 100 μm×100 μm region with a scanning ion microscope. ６ Sn ５ When an alloy is present, it is imaged as white, so using image processing software, the ratio of the area of ​​the white area to the total area of ​​the measurement region was regarded as the exposed area ratio of the copper-tin alloy layer.

[0078] [Cu ６ Sn ５ Alloy layer and Cu ３ Measurement method for volume ratio of Sn alloy layer] Cu of copper-tin alloy layer ６ Sn ５ Alloy layer and Cu ３ The volume ratio of the Sn alloy layer was measured by observing the cross section with a scanning ion microscope. As a measurement method, 50 lines were drawn in the thickness direction (depth direction) for each cross section of three fields of view. ６ Sn ５ Alloy layer, Cu ３ The length was measured at the location of the Sn alloy layer, and the height was calculated from the average value. ６ Sn ５ Alloy layer, Cu ３ For each Sn alloy layer, one line was drawn through the longest point 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 is approximately equal to the area ratio.

[0079] [Method for measuring arithmetic mean curvature Spc of peaks] Observation was performed over 10 fields of view using a laser microscope (Keyence Corporation 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.

[0080] [Method for measuring dynamic friction coefficient and stability] 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 to simulate the contact area between the male and female terminals of a mating connector. Using a friction measuring machine (horizontal load tester, model M-2152ENR) manufactured by Aikoh 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 10 mm horizontally at a sliding speed of 80 mm / min to measure the friction force, thereby determining the dynamic friction coefficient. A dynamic friction coefficient of 0.3 or less was rated as pass (A), and one exceeding this was rated as fail (B).

[0081] 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 as stability "A," and those whose measurements were within ±25% or more were rated as stability "B."

[0082] [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 50 g.

[0083] The results are shown in Table 2.

[0084]

[0085] 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.

[0086] In contrast, in Comparative Example 1, the primary cooling air volume 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.

[0087] 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, which increased the true contact area and made adhesion more likely to occur, 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.

[0088] The present invention can be used as a plated copper terminal material useful as a terminal for connectors used to connect electrical wiring in automobiles, consumer devices, etc., particularly as a terminal for multi-pin connectors.

[0089] REFERENCE SIGNS LIST 1 Coated copper terminal material 2 Substrate 3 Nickel layer 4 Copper-tin alloy layer 5 Tin layer 6 Coating 7 Cu ３ Sn alloy layer 8 Cu ６ Sn ５ Alloy layer 11 Plated material 12 Nickel plating layer 13 Copper plating layer 14 Tin plating layer

Claims

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 0.20 μm or more and 1.20 μm or less, the nickel layer has an average thickness of 0.05 μm or more and 2.00 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%.

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.

3. The copper-tin alloy layer is a Cu layer disposed on at least a portion of the nickel layer. ３ The Sn alloy layer and the Cu layer on the nickel layer ３ On the Sn alloy layer, and ３ The Cu layer is formed so as to extend over the nickel layer where no Sn alloy layer is present. ６ Sn ５ and an alloy layer, ６ Sn ５ Cu for alloy layer ３ 2. The plated copper terminal material according to claim 1, wherein the volume ratio of the Sn alloy layer is 20% or less.

4. The copper-tin alloy layer is a Cu layer disposed on at least a portion of the nickel layer. ３ The Sn alloy layer and the Cu layer on the nickel layer ３ On the Sn alloy layer, and ３ The Cu layer is formed so as to extend over the nickel layer where no Sn alloy layer is present. ６ Sn ５ and an alloy layer, ６ Sn ５ Cu for alloy layer ３ 3. The plated copper terminal material according to claim 2, wherein the volume ratio of the Sn alloy layer is 20% or less.

5. A method for manufacturing a copper terminal material with a plating film formed on a substrate made of copper or a copper alloy, the method comprising 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, the thickness of the nickel plating layer being 0.05 μm or more and 2.00 μm or less, the thickness of the copper plating layer being 0.05 μm or more and 0.40 μm or less, and the thickness of the tin plating layer being 0.50 μm or more and 1.50 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, 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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