JP6217390B2 - Tin-plated copper alloy terminal material with excellent insertability - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a tin-plated copper alloy terminal material useful as a connector terminal used for connecting electrical wiring of automobiles, consumer devices, etc., particularly as a terminal for a multi-pin connector.

The tin-plated copper alloy terminal material is a material in which a CuSn alloy layer is formed under the Sn-based surface layer of the surface layer by performing reflow treatment after applying Cu plating and Sn plating on a copper alloy base material. Yes, it is widely used as a terminal material.
2. Description of the Related Art In recent years, for example, automobiles have rapidly become electrically equipped, and the number of circuits of electrical equipment increases accordingly. Therefore, the size of the connector to be used and the increase in the number of pins have become remarkable. When the number of connectors is increased, even if the insertion force per single pin is small, a large force is required for the entire connector when the connector is inserted, and there is a concern that the productivity is lowered. Therefore, attempts have been made to reduce the insertion force per single pin by reducing the friction coefficient of the tin-plated copper alloy material.

For example, there is one that reduces the insertion force by forming a metal layer having a crystal structure different from tin on the outermost surface of the Sn-plated copper alloy material (Patent Document 1), but the contact resistance increases, solder wettability There has been a problem of lowering.
In Patent Document 2, the surface plating layer is a layer obtained by reflowing or thermally diffusing a Sn plating layer and a plating layer containing Ag or In.
Patent Document 3 discloses that an Sn-Ag alloy layer is formed by forming an Ag plating layer on the Sn plating layer and performing heat treatment.
These techniques described in Patent Documents 2 and 3 are all heat-treated to form an Sn alloy layer, and the entire surface is covered with a hard Sn alloy layer. Therefore, when used for both male and female terminals, Although there is an effect of reducing frictional resistance, there is a problem that abrasive wear occurs when the terminal on one side is a general-purpose Sn-plated terminal material.
Here, the insertion force F of the connector is such that the force (contact pressure) by which the female terminal presses the male terminal is P, and the dynamic friction coefficient is μ. 2 × μ × P. In order to reduce this F, it is effective to reduce P, but in order to ensure the electrical connection reliability of the male and female terminals when the connector is fitted, the contact pressure cannot be reduced unnecessarily. About 3N is required. Some multi-pin connectors exceed 50 pins / connector, but the insertion force of the entire connector is preferably 100 N or less, preferably 80 N or less, or 70 N or less, so that the dynamic friction coefficient μ is required to be 0.3 or less. The

Japanese Patent Laid-Open No. 11-102739 JP 2007-177329 A Japanese Patent Laid-Open No. 2004-2225070

  Conventionally, Sn plated materials with reduced surface frictional resistance have been developed, many of which are effective in reducing frictional resistance between the same kind of Sn plated materials. However, in reality, in the case of a connection terminal for fitting a male and female terminal, the same material type is rarely used for both, and in particular, a general-purpose Sn-plated terminal material based on brass is widely used for the male terminal. It has been. Therefore, even if a low insertion force terminal material is used only for the female terminal, there is a problem that the effect of reducing the insertion force is small.

  The present invention has been made in view of the above-described problems, and is a tin-plated copper alloy terminal material that can reduce the insertion force at the time of fitting even to a terminal using a general-purpose Sn-plated terminal material. For the purpose of provision.

The inventors have controlled the shape of the interface between the CuSn alloy layer and the Sn-based surface layer as a means for lowering the frictional resistance of the surface layer of the terminal material, and placed a steep uneven CuSn alloy layer directly under the Sn-based surface layer. It has been found that the friction coefficient is reduced by doing so. However, when this low insertion force terminal material was used for only one of the terminals and the other was a general-purpose Sn plating material, the effect of reducing the friction coefficient was reduced by half.
In any case, since the outermost surface is Sn plating, Sn adhesion occurs when Sn of the same kind is in contact with each other, and the effect of reducing the friction coefficient is halved. In particular, since the low insertion force terminal material has a hard CuSn alloy layer disposed immediately below the Sn-based surface layer, it is considered that Sn of the soft Sn plating layer of the general-purpose Sn plating terminal material is scraped and adhered.
As a result of intensive research, the inventors have formed a thin Ag coating layer on the outermost surface, thereby ensuring the effect of reducing the friction coefficient of the low insertion force terminal material, and further suppressing the adhesion of Sn, and the other terminal. It was found that the frictional resistance can be reduced even by using a general-purpose material.

That is, in the tin-plated copper alloy terminal material of the present invention, an Sn-based surface layer is formed on the surface of a base material made of Cu or Cu alloy, and the Sn-based surface layer is interposed between the Sn-based surface layer and the base material. A tin-plated copper alloy terminal material in which a CuSn alloy layer / NiSn alloy layer / Ni or Ni alloy layer is formed in order from the surface layer, wherein the CuSn alloy layer is mainly composed of Cu ₆ Sn ₅ , and the Cu ₆ Sn ₅ is a compound alloy layer partially replaced by Ni of Cu, the NiSn alloy layer is mainly composed of _Ni 3 Sn _4, compound alloy layer a portion of Ni of the _Ni 3 Sn ₄ has been substituted with Cu The average distance S between the local peaks of the CuSn alloy layer is not less than 0.8 μm and not more than 2.0 μm, and the average thickness of the Sn-based surface layer is not less than 0.2 μm and not more than 0.6 μm, and the Sn-based 0.05μm or less on the outermost surface of the surface layer An Ag coating layer having a thickness of 5 mm is formed, and the dynamic friction coefficient of the surface is 0.3 or less.

The average distance S between the local peaks of the CuSn alloy layer is 0.8 μm or more and 2.0 μm or less, the average thickness of the Sn system surface layer is 0.2 μm or more and 0.6 μm or less, and 0.05 μm or less on the outermost surface of the Sn system surface layer. By providing this Ag coating layer, the dynamic friction coefficient can be reduced to 0.3 or less even for a general-purpose Sn-plated terminal material. In this case, (Cu, Ni) ₆ Sn ₅ layer (CuSn alloy layer) in which a part of Cu is replaced with Ni and (Ni, Cu) ₃ Sn ₄ layer (NiSn alloy layer) in which a part of Ni is replaced with Cu Due to the presence of, an average interval S between the local peaks of the CuSn alloy layer becomes a steep uneven shape with a diameter of 0.8 to 2.0 μm. In addition, the average thickness of the Sn-based surface layer is set to 0.2 μm or more and 0.6 μm or less because if the thickness is less than 0.2 μm, the solder wettability and the electrical connection reliability are deteriorated. This is because the surface layer cannot be made of a composite structure of Sn and CuSn alloy and is occupied only by Sn, so that the dynamic friction coefficient increases. A more preferable average thickness of the Sn-based surface layer is 0.3 μm or more and 0.5 μm or less.
When the film thickness of the Ag coating layer exceeds 0.05 μm, it is possible to simultaneously obtain the friction coefficient reduction effect due to the special interface shape between the Sn-based surface layer and the CuSn alloy layer and the Sn adhesion suppression effect due to the Ag coating layer. In addition, since only the adhesion suppression effect by the Ag coating layer is obtained, a sufficient friction coefficient reduction effect cannot be obtained, and the thicker the Ag coating layer, the higher the cost. The thickness of the Ag coating layer is preferably 0.005 μm or more.
Here, the dynamic friction coefficient of the surface is 0.3 or less for the general-purpose Sn plating terminal material having the Sn plating layer on the outermost surface as well as between the tin plating copper alloy terminal materials of the present invention. Is done. A general-purpose Sn-plated terminal material having an Sn plating layer on the outermost surface is obtained by subjecting a base material to Cu plating and Sn plating and reflow treatment, and an average interval S between local peaks of a CuSn alloy layer is 0.00. Sn plating terminal material having an Sn plating layer with an average thickness of 0.2 μm or more and 3 μm or less on the outermost surface, or a thickness of 0.5 μm or more and 3 μm or less on the substrate without reflow treatment. The Sn plating terminal material which formed Sn plating layer is said.

In the tin-plated copper alloy terminal material of the present invention, the CuSn alloy layer may contain 1 at% or more and 25 at% or less of Ni in the Cu ₆ Sn ₅ .
The reason why the Ni content is defined as 1 at% or more is that if it is less than 1 at%, a compound alloy layer in which a part of Cu of Cu ₆ Sn ₅ is substituted with Ni is not formed, and a steep uneven shape is not obtained. If the amount exceeds 25 at%, the shape of the CuSn alloy layer tends to be too fine, and if the CuSn alloy layer becomes too fine, the dynamic friction coefficient may not be 0.3 or less. Because there is.

  According to the present invention, an Ag coating layer having a thickness of 0.05 μm or less is formed on the outermost surface of the Sn-based surface layer of the low insertion force terminal material in which the uneven shape of the interface between the CuSn metal layer and the Sn-based surface layer is controlled. As a result, even when used in combination with a general-purpose Sn-plated terminal material, the insertion force at the time of fitting can be reduced.

It is sectional drawing which shows typically the tin plating copper alloy terminal material of this invention. It is sectional drawing of the fitting part which shows the example of the fitting type connection terminal to which the terminal material of this invention is applied. It is sectional drawing which shows typically the terminal material used for a male terminal. It is a front view which shows notionally the apparatus for measuring a dynamic friction coefficient. It is a STEM image of the cross section of the copper alloy terminal material of Example 6. It is an EDS analysis figure along the white line part of FIG. It is a STEM image of the cross section of the copper alloy terminal material of the comparative example 7. It is an EDS analysis figure which follows the white line part of FIG. It is a microscope picture of the male terminal test piece surface of Example 2 after a dynamic friction coefficient measurement. It is a microscope picture of the male terminal test piece surface of the comparative example 1 after a dynamic friction coefficient measurement. It is a microscope picture of the male terminal test piece surface of the comparative example 3 after a dynamic friction coefficient measurement.

The tin plating copper alloy terminal material of embodiment of this invention is demonstrated.
In the tin-plated copper alloy terminal material of this embodiment, as schematically shown in FIG. 1, the Sn-based surface layer 6 is formed on the surface of the base material 5 made of Cu or Cu alloy. CuSn alloy layer 7 / NiSn alloy layer 8 / Ni or Ni alloy layer 9 are formed in order from the Sn-based surface layer 6 between the base material 5 and the base material 5, and 0.05 μm or less of Ag is formed on the Sn-based surface layer 6. The coating layer 10 is formed, and the dynamic friction coefficient of the surface is 0.3 or less.

If a base material consists of Cu or Cu alloy, the composition in particular will not be limited.
The Ni or Ni alloy layer is a layer made of Ni alloy such as pure Ni, Ni—Co, or Ni—W.
The CuSn alloy layer is a compound alloy layer in which Cu ₆ Sn ₅ is the main component and a part of Cu in Cu ₆ Sn ₅ is substituted with Ni. The NiSn alloy layer is mainly composed of Ni ₃ Sn ₄ and Ni ₃ This is a compound alloy layer in which a part of Ni in Sn ₄ is replaced with Cu. These compound layers are formed by sequentially forming a Ni plating layer, a Cu plating layer, and a Sn plating layer on a base material, as will be described later, and performing a reflow treatment on the Ni or Ni alloy layer. The NiSn alloy layer and the CuSn alloy layer are formed in this order.
Further, the interface between the CuSn alloy layer and the Sn-based surface layer is formed in a steep uneven shape, and the average interval S between the local peaks of the CuSu alloy layer is 0.8 μm or more and 2.0 μm or less. The average interval S between the local peaks is extracted from the roughness curve by the reference length in the direction of the average line, the length of the average line corresponding to the adjacent local peaks is obtained, and is determined within the range of the reference length. It is the average between many local peaks. It can be determined by measuring the surface of the CuSn alloy layer after removing the Ag coating layer and the Sn-based surface layer with an etching solution.
Further, the average thickness of the Sn-based surface layer is 0.2 μm or more and 0.6 μm or less, and an Ag coating layer of 0.05 μm or less, preferably 0.005 μm or more is formed on the outermost surface of the Sn-based surface layer. .

In the terminal material having such a structure, a part of Ni is substituted with Cu under a (Cu, Ni) ₆ Sn ₅ layer (CuSn alloy layer) in which a part of Cu is substituted with Ni (Ni, Cu) _3. Due to the presence of the Sn ₄ layer (NiSn alloy layer), the average interval S between the local peaks of the CuSn alloy layer becomes a steep uneven shape of 0.8 μm or more and 2.0 μm or less, and several hundred nm from the surface of the Sn-based surface layer. In this depth range, a composite structure of a hard CuSn alloy layer and an Sn-based surface layer is obtained.
In this case, the Ni content in Cu ₆ Sn ₅ is 1 at% or more and 25 at% or less. The reason why the Ni content is defined as 1 at% or more is that if it is less than 1 at%, a compound alloy layer in which a part of Cu of Cu ₆ Sn ₅ is substituted with Ni is not formed, and a steep uneven shape is not obtained. If the amount exceeds 25 at%, the shape of the CuSn alloy layer tends to be too fine, and if the CuSn alloy layer becomes too fine, the dynamic friction coefficient may not be 0.3 or less. Because there is.
On the other hand, the content of Cu in the Ni ₃ Sn ₄ alloy layer is preferably 5 at% or more and 20 at% or less. The condition that the Cu content is low means that the amount of Ni contained in Cu ₆ Sn ₅ is also reduced (when Ni is not substituted in Ni ₃ Sn ₄ , Ni is substituted into Cu ₆ Sn _5. Rarely) The reason why the upper limit is set is that Cu exceeding 20% does not actually enter Ni ₃ Sn ₄ .

  The average thickness of the Sn-based surface layer is set to 0.2 μm or more and 0.6 μm or less because if it is less than 0.2 μm, solder wettability and electrical connection reliability are reduced. This is because a composite structure of Sn and a CuSn alloy cannot be formed and the dynamic friction coefficient increases because it is occupied only by Sn. A more preferable average thickness of the Sn-based surface layer is 0.3 μm or more and 0.5 μm or less.

  The Ag coating layer is a coating layer made of Ag, and is formed on the Sn-based surface layer after the reflow treatment as described later, and has a film thickness of 0.05 μm or less. When the film thickness exceeds 0.05 μm, the friction coefficient reduction effect due to the special interface shape between the Sn-based surface layer and the CuSn alloy layer and the Sn adhesion suppression effect due to the Ag coating layer cannot be obtained at the same time. The effect of reducing the friction coefficient is not obtained because of only the effect of suppressing adhesion due to, and the higher the Ag coating layer, the higher the cost. The thickness of the Ag coating layer is preferably 0.005 μm or more.

Next, the manufacturing method of this terminal material is demonstrated.
As a base material, a plate material made of Cu or Cu alloy such as Cu-Ni-Si is prepared. After the surface of the plate material is cleaned by degreasing, pickling, etc., the base Ni plating, Cu plating, and Sn plating are applied in this order.
The base Ni plating may be a general Ni plating bath. For example, a sulfuric acid bath mainly composed of sulfuric acid (H ₂ SO ₄ ) and nickel sulfate (NiSO ₄ ) may be used. The temperature of the plating bath is 20 ° C. or more and 50 ° C. or less, and the current density is 1 to 30 A / dm ² or less. The thickness of the underlying Ni plating layer is 0.05 μm or more and 1.0 μm or less. If it is less than 0.05 μm, the Ni content contained in the (Cu, Ni) ₆ Sn ₅ alloy is reduced, and a steep uneven CuSn alloy layer is not formed. It is to become.
For Cu plating, a general Cu plating bath may be used. For example, a copper sulfate bath mainly composed of copper sulfate (CuSO ₄ ) and sulfuric acid (H ₂ SO ₄ ) may be used. The temperature of the plating bath is 20 to 50 ° C., and the current density is 1 to 30 A / dm ² . The film thickness of the Cu plating layer formed by this Cu plating is 0.05 μm or more and 0.20 μm or less. If it is less than 0.05 μm, the Ni content contained in the (Cu, Ni) ₆ Sn ₅ alloy becomes large, the shape of the CuSn alloy layer becomes too fine, and if it exceeds 0.20 μm, (Cu, Ni) _{This is because} the Ni content in the ₆ Sn ₅ alloy is reduced, and a steep uneven CuSn alloy layer is not formed.
As a plating bath for forming the Sn plating layer, a general Sn plating bath may be used. For example, a sulfuric acid bath mainly composed of sulfuric acid (H ₂ SO ₄ ) and stannous sulfate (SnSO ₄ ) is used. Can do. The temperature of the plating bath is 15 to 35 ° C., and the current density is 1 to 30 A / dm ² . The film thickness of this Sn plating layer shall be 0.5 micrometer or more and 1.0 micrometer or less. When the thickness of the Sn plating layer is less than 0.5 μm, the Sn-based surface layer after reflow is thinned and the electrical connection characteristics are impaired. When the thickness exceeds 1.0 μm, the surface layer portion has a composite structure of Sn and CuSn alloy. It is difficult to make the friction coefficient 0.3 or less.

As reflow treatment conditions, the substrate is heated for 1 second to 12 seconds in a reducing atmosphere under the condition that the surface temperature of the base material is 240 ° C. or higher and 360 ° C. or lower, and then rapidly cooled. More preferably, it is rapid cooling after heating at 260 to 300 ° C. for 5 to 10 seconds. In this case, as shown below, the holding time has an appropriate time in the range of 1 second to 12 seconds depending on the thickness of each of the Cu plating layer and the Sn plating layer, and the holding time is less as the plating thickness is thinner, Longer holding times are required as the thickness increases.
<Holding time after raising substrate temperature to 240 ° C. or higher and 360 ° C. or lower>
(1) When the thickness of the Sn plating layer is 0.5 μm or more and less than 0.7 μm, when the thickness of the Cu plating layer is 0.05 or more and less than 0.16 μm, the thickness of the Cu plating layer is 1 second or more and 6 seconds or less. Is 0.16 μm or more and 0.20 μm or less, 3 seconds or more and 9 seconds or less. (2) The thickness of the Cu plating layer is 0.05 or more and 0 or less, whereas the thickness of the Sn plating layer is 0.7 μm or more and 1.0 μm or less. When the thickness is less than 16 μm, it is 3 seconds or more and 9 seconds or less. When the thickness of the Cu plating layer is 0.16 μm or more and 0.20 μm or less, the temperature is 6 seconds or more and 12 seconds or less. When the heating time is less than the time shown in 2), the dissolution of Sn does not proceed, and when the heating temperature exceeds 360 ° C. and the holding time exceeds the time shown in (1) and (2), crystals in the CuSn alloy layer grow greatly. The desired shape cannot be obtained, and the CuSn alloy layer Sn-based surface layer reaches the surface layer is because the longer remaining. Moreover, when heating conditions are high, the oxidation of the Sn-based surface layer proceeds, which is not preferable.

  A material such as degreasing and pickling is performed on the material after the reflow treatment to clean the surface, and then an Ag coating layer is formed by a sputtering method or a plating method. The film thickness is set to 0.05 μm or less as described above.

And this terminal material is shape | molded, for example in the female terminal 2 of a shape as shown in FIG.
In the example shown in FIG. 2, the female terminal 2 is formed in a rectangular tube shape as a whole, and the male terminal 1 is sandwiched from both sides by fitting the male terminal 1 from the opening 15 at one end thereof. It is connected in a state. Inside the female terminal 2, an elastically deformable contact piece 16 that is brought into contact with one surface of the fitted male terminal 1 is provided, and a male terminal is provided on the side wall 17 facing the contact piece 16. The hemispherical convex part 18 which contacts the other surface of 1 is formed in the state which protruded inward by embossing. The contact piece 16 is also provided with a mountain-folded bent portion 19 so as to face the convex portion 18. The protruding portion 18 and the bent portion 19 protrude so as to protrude toward the male terminal 1 when the male terminal 1 is fitted, and become the sliding portion 11 with respect to the male terminal 1.

As shown schematically in FIG. 3, the terminal material used for the male terminal 1 has an Sn plating layer 22 formed on the upper surface of a base material 21 made of a Cu alloy, and the Sn plating layer 22 and the Cu alloy base material 21. And a general reflow treatment material in which a CuSn alloy layer 23 is formed. In this male terminal 1, the average interval S between the local peaks of the CuSn alloy layer 23 measured when the Sn plating layer 22 is dissolved and removed and the CuSn alloy layer 23 appears on the surface is less than 0.8 μm or 2 The average thickness of the Sn plating layer 22 is not less than 0.2 μm and not more than 3 μm.
The male terminal 1 is formed in a flat plate shape, and is formed by subjecting a copper alloy plate to Cu plating and Sn plating in this order, and then reflow treatment. In this case, as a heating condition for the reflow treatment, in general, it is rapidly cooled after being held at a temperature of 240 ° C. or higher and 400 ° C. or lower for a time of 1 second or longer and 20 seconds or shorter.
In addition, it is good also considering the terminal material which formed Sn plating layer with an average thickness of 0.5 micrometer or more and 3 micrometers or less by Sn plating to the base material which consists of Cu alloy, without performing reflow processing as a male terminal material.

When the male terminal 1 is inserted between the contact piece 16 and the side wall 17 from the opening 15 of the female terminal 2 in the connector formed using such female terminal material and male terminal material, the contact piece 16 becomes a two-dot chain line. Is elastically deformed from the position indicated by the solid line to the position indicated by the solid line, and the male terminal 1 is held between the bent part 19 and the convex part 18.
As described above, in the female terminal 2, the interface between the CuSn alloy layer and the Sn-based surface layer is formed in a steep concavo-convex shape in which the average interval S between the local peaks of the CuSn alloy layer is 0.8 μm or more and 2.0 μm or less. In addition, since the average thickness of the Sn-based surface layer is 0.1 μm or more and 0.6 μm or less, and the Ag coating layer having a thickness of 0.05 μm or less is formed on the outermost surface of the Sn-based surface layer, The adhesion of Sn to the surface of the part 18 and the bent part 19 is suppressed, and the effect of reducing the dynamic friction coefficient due to the steep uneven shape of the interface between the CuSn alloy layer and the Sn-based surface layer is effective. Even if the male terminal 1 is of an Sn-based surface layer by a normal reflow process, the dynamic friction coefficient can be reduced to 0.3 or less.

An oxygen-free copper plate having a plate thickness of 0.25 mm was used as a base material, and base Ni plating, Cu plating, and Sn plating were sequentially applied. In this case, the plating conditions for Cu plating and Sn plating are the same in both the examples and the comparative examples. After the plating treatment, both the examples and the comparative examples were subjected to reflow treatment, and the substrate surface temperature was raised to a temperature of 240 ° C. or higher and 360 ° C. or lower in a reducing atmosphere, and held for 1 second or longer and 12 seconds or shorter. After that, it was cooled with water. After the reflow treatment, an Ag coating layer was formed by a sputtering method.
As comparative examples, the thickness of the base Ni plating, the thickness of the Cu plating, the thickness of the Sn plating, and the case where the Ag coating layer was not formed were also prepared.
In this case, the conditions of each plating were as shown in Table 1. In Table 1, Dk is an abbreviation of cathode current density and ASD is A / dm ² .
The thickness of each plating layer and the reflow conditions were as shown in Table 2.

For these samples, the thickness of the Sn-based surface layer after reflow, the thickness of the CuSn alloy layer, the Ni content in (Cu, Ni) ₆ Sn ₅ , the presence or absence of the (Ni, Cu) ₃ Sn ₄ layer, the CuSn alloy layer The average interval S of the local summits, the thickness of the Ag coating layer, the dynamic friction coefficient, and the solder wettability were evaluated.
The thickness of the Ag coating layer, the Sn-based surface layer after reflowing, and the thickness of the CuSn alloy layer were measured with a fluorescent X-ray film thickness meter (SFT9400) manufactured by SII Nanotechnology. The thickness of the Sn-based surface layer and the CuSn alloy layer after the reflow is measured with respect to the sample before forming the Ag coating layer, after first measuring the thickness of all the Sn-based surface layers of the sample after the reflow, The Sn-based surface layer is removed by immersing in an etching solution for removing the plating film composed of a component that does not corrode CuSn alloy by etching pure Sn, such as L80, and the underlying CuSn alloy layer is exposed to be pure. After measuring the thickness of the CuSn alloy layer in terms of Sn, (thickness of all Sn-based surface layer−thickness of CuSn alloy layer in terms of pure Sn) was defined as the thickness of the Sn-based surface layer.
The Ni content in the (Cu, Ni) ₆ Sn ₅ layer and the presence or absence of the (Ni, Cu) ₃ Sn ₄ layer were determined by a cross-sectional STEM image and EDS line analysis.
The average distance S between the local peaks of the CuSn alloy layer is immersed in an etching solution for removing the Sn plating film to remove the Sn-based surface layer, and the underlying CuSn alloy layer is exposed. Using (VK-X200), it was obtained from the average value of S measured at 10 points in total, 5 points in the longitudinal direction and 5 points in the short direction, under the condition of 150 times the objective lens (measuring field of view 96 μm × 72 μm).

For the dynamic friction coefficient, a plate-shaped male terminal test piece and a hemispherical female test piece having an inner diameter of 1.5 mm were used for each sample so as to simulate the contact portion of the male terminal and female terminal of the fitting type connector. The friction coefficient between the two test pieces was measured by using a friction measuring machine (μV1000) manufactured by Trinity Lab Co., Ltd. to obtain a dynamic friction coefficient. Referring to FIG. 4, a male terminal test piece 32 is fixed on a horizontal base 31, a hemispherical convex surface of a female test piece 33 is placed thereon, and the plating surfaces are brought into contact with each other. The load P is applied and the male terminal test piece 32 is pressed. With this load P applied, the frictional force F when the male terminal test piece 32 was pulled 10 mm in the horizontal direction indicated by the arrow at a sliding speed of 80 mm / min was measured by the load cell 35. A dynamic friction coefficient (= Fav / P) was obtained from the average value Fav of the friction force F and the load P. Table 2 shows the dynamic friction coefficient when the load is 4.9 N (500 gf).
As a male terminal test piece, a copper alloy (C2600, Cu: 70% by volume-Zn: 30% by mass) having a plate thickness of 0.25 mm was used as a base material, and Cu plating and Sn plating were performed in this order and reflow treatment was performed. The reflow conditions for this male terminal material were a substrate temperature of 270 ° C. and a holding time of 6 seconds, the thickness of the Sn plating layer after reflow was 0.6 μm, and the thickness of the CuSn alloy layer was 0.5 μm. The average distance S between the local peaks of the CuSn alloy layer was 2.1 μm.

About solder wettability, the test piece was cut out to 10 mm width, and the zero crossing time was measured by the meniscograph method using the active flux. (Measured under the condition of immersion in Sn-3% Ag-0.5% Cu solder with a solder bath temperature of 230 ° C. and immersion rate of 2 mm / sec, immersion depth of 1 mm, and immersion time of 10 sec.) The case of less than 2 seconds was evaluated as ◯, and the case of exceeding 3 seconds was evaluated as ×.
Moreover, in order to evaluate electrical reliability, it heated at 150 degreeC * 500 hours in air | atmosphere, and contact resistance was measured. The measuring method is based on JIS-C-5402, 4 terminal contact resistance tester (manufactured by Yamazaki Seiki Laboratories: CRS-113-AU), sliding type (1mm) load change from 0 to 50g-contact resistance Was evaluated by the contact resistance value when the load was 50 g.
These measurement results and evaluation results are shown in Table 2.

As is apparent from Table 2, all the examples had a small coefficient of dynamic friction of 0.3 or less, good solder wettability, and a contact resistance of 10 mΩ or less. Particularly, Examples 1 to 8 and 10 to 19 having Ni plating thicknesses of 0.1 μm or more all exhibited low contact resistance of 4 mΩ or less.
On the other hand, the following problems were recognized in each comparative example. Since Comparative Examples 1 and 3 do not have an Ag coating layer, the dynamic friction coefficient is large. In Comparative Example 2, there is no (Ni, Cu) ₃ Sn ₄ layer, and only by forming an Ag coating layer, although there is a reduction effect, a great effect cannot be obtained. In Comparative Example 4, since the film thickness of the Ag coating layer is large, the effect of reducing the dynamic friction coefficient by the CuSn alloy layer cannot be sufficiently obtained, and the dynamic friction coefficient exceeds 0.3. In Comparative Example 5, since the Cu plating thickness is too thin, the average interval S 1 between the local peaks of the CuSn alloy layer falls below the lower limit, and the dynamic friction coefficient exceeds 0.3. In Comparative Examples 6, 8, and 9, the CuSn alloy layer grows too much, and the Sn-based surface layer remaining on the surface becomes too small, so that the solder wettability is deteriorated. In Comparative Example 7 in which the dynamic friction coefficient exceeds 0.3, since the Cu plating thickness is too thick, there is no (Ni, Cu) ₃ Sn ₄ layer, and Ni is not contained in Cu ₆ Sn _5. Cannot be obtained.
5 and 6 show the cross-sectional STEM image and EDS line analysis result of Example 6, and FIGS. 7 and 8 show the cross-sectional STEM image and EDS line analysis result of Comparative Example 7, respectively. 5 and 6, (i) is a substrate, (ii) is a Ni layer, (iii) is a (Ni, Cu) ₃ Sn ₄ layer, and (iv) is a (Cu, Ni) ₆ Sn ₅ layer. 7 and 8, (i ′) is a Ni layer, (ii ′) is a Cu ₃ Sn layer, and (iii ′) is a Cu ₆ Sn ₅ layer.
As can be seen from the comparison of these photographs, the example is that Ni is contained in Cu ₆ Sn ₅ as shown in FIG. 6 and at the interface between the Ni layer and the Cu ₆ Sn ₅ layer. It can be seen that a Ni ₃ Sn ₄ layer containing Cu is formed. The Cu content in the Ni ₃ Sn ₄ layer in the terminal material of the example is assumed to be in the range of 5 to 20 at%. For example, in Example 2, it was 11 at%.
In the comparative example, as shown in FIG. 8, the Ni ₃ Sn ₄ layer is not formed, and it is understood that Ni is not contained in Cu ₆ Sn ₅ .
9 is a micrograph of the sliding surface of the male terminal test piece after measurement of the dynamic friction coefficient of Example 2, FIG. 10 is a micrograph of Comparative Example 1, and FIG. 11 is a micrograph of Comparative Example 7. As can be seen from comparison of these photographs, in the example, Sn adhesion was suppressed and the sliding surface was smooth, whereas in the comparative example, the sliding surface was rough due to Sn adhesion. In Comparative Example 7, in which the average interval S between the local peaks on the female side is large, Sn adhesion occurs and the sliding surface is rough even if there is an Ag coating layer.

DESCRIPTION OF SYMBOLS 1 Male terminal 2 Female terminal 5 Base material 6 Sn type | system | group surface layer 7 CuSn alloy layer 8 NiSn alloy layer 9 Ni or Ni alloy layer 10 Ag coating layer 11 Sliding part 15 Opening part 16 Contact piece 17 Side wall 18 Convex part 19 Bending part 21 Substrate 22 Sn plating layer 23 CuSn alloy layer 31 units 32 Male terminal test piece 33 Female test piece 34 Weight 35 Load cell

Claims (2)

An Sn-based surface layer is formed on the surface of the base material made of Cu or Cu alloy, and the Cu-based alloy layer / NiSn alloy layer / Ni are arranged in this order from the Sn-based surface layer between the Sn-based surface layer and the base material. Alternatively, a tin-plated copper alloy terminal material on which a Ni alloy layer is formed, wherein the CuSn alloy layer has Cu ₆ Sn ₅ as a main component, and a part of Cu in the Cu ₆ Sn ₅ is substituted with Ni. The NiSn alloy layer is a compound alloy layer containing Ni ₃ Sn ₄ as a main component, and a part of Ni in the Ni ₃ Sn ₄ is replaced with Cu, and an average interval between local peaks of the CuSn alloy layer S is 0.8 μm or more and 2.0 μm or less, and the average thickness of the Sn-based surface layer is 0.2 μm or more and 0.6 μm or less, and the film thickness is 0.05 μm or less on the outermost surface of the Sn-based surface layer. An Ag coating layer of the surface is formed, A tin-plated copper alloy terminal material having a dynamic friction coefficient of 0.3 or less. 2. The tin-plated copper alloy terminal material according to claim 1, wherein the CuSn alloy layer contains 1 at% or more and 25 at% or less of Ni in the Cu ₆ Sn ₅ .