JP6825360B2 - Plated copper terminal material and terminals - Google Patents

Description

The present invention relates to a plated copper terminal material useful as a connector terminal used for connecting electrical wiring of automobiles, consumer devices, etc., and a terminal manufactured by using the plated copper terminal material.

As the terminal for a connector used for connecting an electric wiring of an automobile or a consumer device, a plated copper terminal material in which the surface of a copper or copper alloy base material is plated with tin, gold, silver or the like is generally used. Of these, terminal materials plated with precious metals such as gold and silver are suitable for use in high-temperature environments because they have excellent heat resistance.
Conventionally, as a terminal material plated with such a precious metal, there is one disclosed in the following patent documents.

Patent Document 1 describes that a silver-plated terminal is formed on the surface of a base material made of copper or a copper alloy on a first silver-plated layer on the lower layer side, which is the base material side, and a first silver-plated layer. A terminal material having a two-layered silver-plated layer composed of a second silver-plated layer on the upper layer side exposed on the surface is disclosed, and diffusion to the copper surface is suppressed, so that terminals can be inserted and removed well. It is stated that it has excellent wear resistance.

Patent Document 2 describes that in a silver plating solution containing 80 to 110 g / L of silver, 70 to 160 g / L of potassium cyanide and 55 to 70 mg / L of selenium, a liquid temperature of 12 to 24 ° C. and a current density of 3 to 8 A / L. performing electroplating range product is below 840g · a / L · dm ² concentration and the current density of potassium cyanide and silver plating solution in dm ^2, by forming a surface layer made of silver on the material, surface The preferential orientation plane is the {111} plane, which is half of the X-ray diffraction peak of the {111} plane after heating with respect to the half-value width of the X-ray diffraction peak of the {111} plane before heating at 50 ° C. for 168 hours. It is disclosed that a silver-plated material having a price range ratio of 0.5 or more is produced, and it is stated that an increase in contact resistance can be prevented while maintaining high hardness.

In Patent Document 3, a base layer made of nickel is formed on a material made of copper or a copper alloy, and a surface layer made of silver having a thickness of 10 μm or less is formed on the surface of the base layer. It is disclosed that the thickness of the surface layer is 2 μm or less, preferably 1.5 μm or less, and the area fraction of the surface layer in the {200} orientation is 15% or more, preferably 25% or more, and the bending workability is good. It is stated that there is.

In Patent Document 4, one or more underlayers of nickel, cobalt, zinc, copper and the like having an average crystal grain size of 0.3 μm or more are formed between the conductive metal substrate and the noble metal layer. A noble metal coating material for electrical contacts has been disclosed, and it is described that it suppresses the diffusion of substrate components in a high temperature environment and has high long-term reliability.

Patent Document 5 describes an alloy-plated intermediate layer containing 0.05 to 20 wt% of phosphorus as a base material of a metallic material and the balance of which is nickel and unavoidable impurities or nickel, cobalt and unavoidable impurities, and silver or silver. A heat-resistant and corrosion-resistant silver plating material having high heat resistance composed of an alloy-plated surface layer is shown.

Japanese Unexamined Patent Publication No. 2008-169408 JP-A-2015-10833 Japanese Unexamined Patent Publication No. 2014-181354 JP 2015-137421 Japanese Unexamined Patent Publication No. 2001-3194

However, in the inventions described in Patent Documents 1 to 3, the terminal characteristics such as contact resistance are improved by optimizing the structure of the silver plating layer, but double plating is required and the composition of the silver plating bath is remarkably high. Due to the limitation, manufacturing becomes complicated. In the invention described in Patent Document 4, the reliability of the noble metal contact is improved by increasing the crystal grain size of the base plating, but since heat treatment is required to enlarge the base plating layer, the copper alloy is used. There is a problem that the structure is also enlarged and the desired material properties cannot be obtained. In the invention described in Patent Document 5, the nickel-based alloy plating film, which is the alloy plating intermediate layer, becomes fine crystals, and copper diffuses to the silver surface through the grain boundaries. Therefore, unless the film thickness is increased, the temperature is as high as 200 ° C. There is a problem that the heat resistance when exposed to is insufficient. In addition, the heat load may cause phosphorus in the nickel alloy plating layer to diffuse to the silver surface, impairing contact reliability. Further, if the nickel or nickel alloy plating layer is thick, the die is consumed severely during pressing. Since the nickel alloy plating layer has poor toughness, if it is thickened, cracks are likely to occur during press working. Therefore, it is desired that the thickness of the nickel alloy plating layer or the like is as thin as possible.

The present invention has been made in view of such circumstances, and an object of the present invention is to manufacture highly reliable terminals and terminal materials at low cost without heat treatment.

In the plated copper terminal material of the present invention, a nickel alloy plating layer and a silver plating layer made of silver or a silver alloy are sequentially laminated on a base material made of copper or a copper alloy, and the nickel alloy plating layer is , Phosphorus or boron is contained in an amount of 0.5% by mass or more and 15% by mass or less, the thickness thereof is 0.05 μm or more and 5.0 μm or less, the average crystal grain size is Rμm, and the thickness is Tμm. × R is 0.05 or more.

In this plated copper terminal material, the nickel alloy plating layer containing phosphorus or boron has heat resistance while preventing the diffusion of copper from the base material, and the silver plating layer has excellent heat resistance. In this case, the heat resistance of silver deteriorates when the diffusion prevention effect of the nickel alloy plating layer is impaired.
The nickel alloy plating layer contains 0.5% by mass or more and 15% by mass or less of phosphorus or boron because it suppresses the diffusion of copper from the base material when phosphorus or boron is less than 0.5% by mass. This is because the effect is not sufficient, and if it exceeds 15% by mass, the film becomes brittle and cracks during processing are likely to occur.
The reason why the thickness of the nickel alloy plating layer is 0.05 μm or more and 5.0 μm or less is that if it is less than 0.05 μm, pinholes are generated in the film and the heat resistance deteriorates. If it exceeds 5.0 μm, cracks occur during bending. Because it does.
The smaller the diffusion path in the nickel alloy plating layer, that is, the longer the distance between the grain boundaries, the more the diffusion of copper can be suppressed. Further, when the thickness of the nickel alloy plating layer is sufficiently thick, the diffusion path of copper becomes long, so that the diffusion of copper can be suppressed. That is, the average crystal grain size Rμm of the nickel alloy plating layer and the thickness Tμm of the nickel alloy plating layer are not sufficient for the number of diffusion paths when T × R is less than 0.05, so that the diffusion of copper is sufficient. Cannot be prevented. When T × R is 0.05 or more, the diffusion paths are sufficiently long with respect to the number of diffusion paths, so that the diffusion of copper can be effectively suppressed.

In the plated copper terminal material of the present invention, it is preferable that a copper plating layer made of copper or a copper alloy is formed between the base material and the nickel alloy plating layer.
By forming the copper plating layer on the surface of the base material, the base of the nickel alloy plating layer becomes smooth, the occurrence of pinholes in the nickel alloy plating layer can be prevented, and the diffusion prevention effect can be enhanced.

In the plated copper terminal material of the present invention, a pure nickel plating layer is formed between the nickel alloy plating layer and the silver plating layer, and the thickness of the pure nickel plating layer is the thickness of the nickel alloy plating layer. It is preferable that it is 0.5 times or more and 5.0 times or less.
Since the nickel alloy plating layer contains phosphorus or boron, when exposed to high temperature, phosphorus or boron in the nickel alloy plating layer diffuses to the surface of the silver plating layer, and the high heat resistance of the silver plating layer, It may impair electrical reliability such as low contact resistance. Therefore, if the pure nickel plating layer is provided between the nickel alloy plating layer and the silver plating layer, the electrical reliability can be improved. If the thickness of the pure nickel plating layer is less than 0.5 times the thickness of the nickel alloy plating layer, the effect of preventing the diffusion of phosphorus or boron is not sufficient, and if it exceeds 5 times, it becomes easily cracked during pressing and the mold is consumed. Becomes fierce.

The terminal of the present invention is made of the plated copper terminal material.

According to the present invention, since a nickel alloy plating layer containing phosphorus or boron is interposed between the base material and the silver plating layer, diffusion of copper from the base material is prevented and excellent heat resistance is exhibited. In this case, a highly reliable plated terminal material can be manufactured at low cost without heat treatment.

It is sectional drawing which simplified the surface part of the terminal material of embodiment.

Hereinafter, embodiments of the present invention will be described.
As shown in FIG. 1, the plated copper terminal material 1 of the present invention has a base material 2 made of copper or a copper alloy plate and a copper plating layer 3 made of copper or a copper alloy formed on the surface of the base material 2. And the nickel alloy plating layer 4 formed on the copper plating layer 3, the pure nickel plating layer 5 formed on the nickel alloy plating layer 4, and the pure nickel plating layer 5 formed on the pure nickel plating layer 5. It has a silver plating layer 6 made of copper or a silver alloy.
As long as the base material 2 is made of copper or a copper alloy, its composition is not particularly limited, but it is preferable that the base material 2 has the processed alteration layer on the surface removed.

The copper plating layer 3 has the effect of smoothing the surface of the base material, and is formed with a thickness of 0.1 μm or more and 1.0 μm or less.
The nickel alloy plating layer 4 is made of an alloy containing phosphorus or boron in nickel, and has an effect of preventing the diffusion of copper from the base material. In this case, the heat resistance is enhanced by containing phosphorus or boron. The content of phosphorus or boron is 0.5% by mass or more and 15% by mass or less, and the thickness is 0.05 μm or more and 5.0 μm or less. Further, assuming that the average crystal grain size is R μm and the thickness is T μm, T × R is 0.05 or more. The larger the T × R, the higher the diffusion prevention effect, the larger the average crystal grain size, and the larger the thickness, the more effective. However, when the average crystal grain size is 5 μm or more, the diffusion path is sufficiently reduced. preferable. The thickness of the nickel alloy plating layer 4 is preferably 0.1 μm or more and 0.5 μm or less.

The average crystal grain size is a line having a length of L μm that crosses 10 or more grain boundaries in parallel with the surface using a scanned ion microscope (SIM) image measured by cross-processing with a focused ion beam (FIB). It was drawn and calculated from the number N where the line parallel to the surface intersected the grain boundary by the following formula. Thirty lines were drawn in any direction, and the average value of the obtained crystal grain sizes was taken as the average crystal grain size.
Average crystal grain size R = L ÷ N (μm)
This average crystal grain size can be varied by controlling the crystal grain size and surface state of the base copper alloy. When nickel-based alloy plating is grown on a base material in which the surface processing alteration layer is removed and the crystal orientation of the surface is appropriately controlled, the nickel-based alloy plating layer grows in alignment with the crystals of the base material, and the base The average crystal grain size can be increased by increasing the crystal grain size of the material.

The pure nickel plating layer 5 has an effect of preventing phosphorus or boron in the nickel alloy plating layer 4 from diffusing to the silver surface, and is formed with a thickness of 0.025 μm or more and 5.0 μm or less. In this case, the thickness of the pure nickel plating layer 5 is preferably 0.5 times or more and 5 times or less with respect to the thickness of the nickel alloy plating layer 4. The purity of the pure nickel plating layer 5 is preferably 99.5% by mass or more.
The combined thickness of the nickel alloy plating layer 4 and the pure nickel plating layer 5 is preferably 1.0 μm or less.
The silver-plated layer 6 has the effect of increasing the heat resistance of the terminal material 1, and the thickness is preferably 0.5 μm or more and 2.0 μm or less.

Next, a method of manufacturing this terminal material will be described.
A copper or copper alloy plate is prepared as the base material, the surface is cleaned, and the surface is etched with a chemical polishing solution in order to enlarge and grow the crystal grains of the copper plating layer formed on the surface of the base material. The processed altered layer on the surface of the base material is removed to expose the crystal plane of the base material to the surface.
Next, each plating layer is laminated on the surface of the base material whose surface has been adjusted in this way by electrolytic plating.
As the plating bath for forming the copper plating layer, a general copper plating bath may be used. For example, a copper sulfate bath containing copper sulfate (CuSO ₄ ) and sulfuric acid (H ₂ SO ₄ ) as main components should be used. Can be done. The temperature of the plating bath is, for example, 20 ° C. or higher and 50 ° C. or lower, and the current density is 1 A / dm ² or higher and 40 A / dm ² or lower.
As the nickel plating bath for forming the nickel alloy plating layer, a general nickel plating bath may be used, and a watt bath containing nickel sulfate (NiSO ₄ ) and boric acid (H ₃ BO ₃ ) as main components, sulfamic acid. A sulfamic acid bath containing nickel (Ni (NH ₂ SO ₃ ) ₂ ) and boric acid (H ₃ BO ₃ ) as main components is used, and in the case of a nickel-phosphorus alloy, phobic acid is added. It is appropriate that the bath temperature is 40 ° C. or higher and 55 ° C. or lower, and the current density is 1 A / dm ² or higher and 40 A / dm ² or lower. However, components such as butynediol and allyl sulfonate that reduce the crystal grain size and brightener components are not used.
As the plating bath for forming the pure nickel plating layer, a watt bath, a sulfamic acid bath and the like are used.
As the plating bath for forming the silver plating layer, a silver cyanide plating bath, which is a general silver plating bath, may be used. The temperature of the bath 15 ℃ than 35 ° C. or less, the current density is 0.1 A / dm ² or more 3A / dm ² or less is appropriate.

The terminal material produced in this way is processed into the shape of a terminal and used. Although connectors such as wiring inside automobiles are exposed to high temperature environments, they have excellent heat resistance and are effective in diffusing copper from the base material because phosphorus or boron is contained in the nickel alloy plating layer that functions as a barrier layer. It is possible to stably maintain excellent characteristics such as high heat resistance and low contact resistance of the silver plating layer. In particular, since the surface of the base material was adjusted by etching and then a copper plating layer was further formed to provide the nickel alloy plating layer, the crystal grains of the nickel alloy plating layer were enlarged, and therefore, the average crystal grain size was increased. The T × R, which is the product of R μm and the thickness T μm, is large, and the diffusion prevention effect is high. Further, since the pure nickel plating layer is formed on the nickel alloy plating layer, it is possible to effectively prevent phosphorus or boron in the nickel alloy plating layer from diffusing to the surface of the silver plating layer, and silver plating. The high electrical reliability of the layer can be reliably maintained.
Moreover, it can be manufactured by a simple method of adjusting the surface of the base material by an etching process and plating, and can be manufactured at low cost.

Using Cu-Zn alloy "MNEX" jointly developed by Mitsubishi Materials Co., Ltd. and Mitsubishi Shindoh Co., Ltd. as the base material, sulfuric acid 100 g / L, hydrogen peroxide 30 g / L, chloride ion 10 mg / L, 1-propanol The copper surface was cleaned by etching with a chemical polishing solution having a composition of 2 mL / L for 20 seconds, and the surface was adjusted so that the copper plating grew in conformity with the crystal grains of the base material.
Then, electrolytic plating was performed at a current density of 2 A / dm ^{2 in} a copper plating bath having a sulfuric acid concentration of 50 g / L and a copper sulfate pentahydrate concentration of 250 g / L at 40 ° C. The copper plating layer by this electrolytic copper plating grew in conformity with the crystal grains of the base material.
Further, using a bath of nickel sulfate hexahydrate 240 g / L, nickel chloride 35 g / L, boric acid 30 g / L, phobic acid 10 g / L, PH = 2.6 on the copper plating layer, nickel phosphorus Alloy plating was formed. Further, a pure nickel plating was formed using a watt bath, and then a silver plating of 1 μm was formed using a cyan bath to obtain a terminal material.

The crystal grain size of the nickel alloy plating layer was controlled by varying the crystal grain size of the base material and allowing the nickel alloy plating to grow consistently on the base material. The substrate was annealed to increase the crystal grain size, and rolling and heat treatment or surface polishing was performed to reduce the crystal grain size.
The crystal grain size is cross-sectioned with a focused ion beam (FIB), and a line with a length of 10 μm is drawn parallel to the surface using a measured scanning ion microscope (SIM) image, and the line parallel to the surface is drawn. It was determined by the line segment method using the number intersecting the grain boundaries.
The thickness of each plating layer was measured with a fluorescent X-ray film thickness meter. Each was measured before the plating layer overlaid was formed.

In addition, the contact resistance and bending workability after heating were evaluated for each sample.
For the contact resistance measurement, a sample having a hemispherical convex portion having a radius of 1.5 mm was prepared, and the hemispherical convex portion was brought into contact with the flat sample using a compression tester having a load cell. In this state, the measurement of the contact resistance between the flat plate sample and the sample having the hemispherical convex portion was started, and the contact load applied between the two was gradually increased. The contact resistance when the load reached 2N was measured using the four-terminal method. The current value at that time was 10 mA. The contact resistance of both the flat plate sample and the sample having the hemispherical convex portion was measured after heating at 200 ° C. for 500 hours.
Regarding bending workability, multiple test pieces with a width of 10 mm and a length of 30 mm were collected from a sample made of strips so that the bending axis was orthogonal to the rolling direction of the base metal, and JCBA (Nippon Bronze). In accordance with the 4 test methods of T307, a W-bending test is performed with a load of 9.8 x 10 ³ N using a W-shaped jig with a bending angle of 90 degrees and a bending radius of 0.5 mm. It was. After that, observation was performed with a stereomicroscope. In the evaluation of bending workability, the level at which no clear cracks were found in the bent part after the test was evaluated as "◎", and although fine cracks were partially generated on the plated surface, the copper alloy base material The level at which no exposure is observed is evaluated as "○", and the level at which the copper alloy base material is not exposed but cracks larger than the level evaluated as "○" are evaluated as "△", and the cracks that occur are evaluated. The level at which the copper alloy base material was exposed was evaluated as "x".
These results are shown in Table 1.

As is clear from this result, the sample No. It is considered that the terminal materials 1 to 7 have a small contact resistance after heating and the diffusion of copper is suppressed. It can also be seen that the bending workability is also good.
On the other hand, sample No. No. 8 has a large contact resistance because it does not have a nickel alloy plating layer containing phosphorus or boron, and sample No. 8 has a large contact resistance. Since T × R of No. 9 is less than 0.05, the contact resistance is large and the bending workability is also inferior. Sample No. In No. 10, the thickness of the nickel alloy plating layer exceeds 5.0 μm, and T × R is less than 0.05, so that the contact resistance is large and the bending workability is also inferior.

1 Copper terminal material with plating 2 Base material 3 Copper plating layer 4 Nickel alloy plating layer 5 Pure nickel plating layer 6 Silver plating layer

Claims (4)

A nickel alloy plating layer and a silver plating layer made of silver or a silver alloy are laminated in this order on a base material made of copper or a copper alloy, and the nickel alloy plating layer contains 0.5% by mass of phosphorus or boron. If the content is 15% by mass or less, the thickness is 0.05 μm or more and 5.0 μm or less, the average crystal grain size is R μm, and the thickness is T μm, T × R is 0.05 or more. Plated copper terminal material characterized by. The plated copper terminal material according to claim 1, wherein a copper plating layer made of copper or a copper alloy is formed between the base material and the nickel alloy plating layer. A pure nickel plating layer is formed between the nickel alloy plating layer and the silver plating layer, and the thickness of the pure nickel plating layer is 0.5 times or more and 5.0 times or less the thickness of the nickel alloy plating layer. The plated copper terminal material according to claim 1 or 2, characterized in that. A plated copper terminal formed of the plated copper terminal material according to any one of claims 1 to 3.

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