WO2016067935A1

WO2016067935A1 - Terminal metal piece and connector

Info

Publication number: WO2016067935A1
Application number: PCT/JP2015/079288
Authority: WO
Inventors: 玄渡邉; 喜文坂; 滋澤田
Original assignee: 株式会社オートネットワーク技術研究所; 住友電装株式会社; 住友電気工業株式会社
Priority date: 2014-10-30
Filing date: 2015-10-16
Publication date: 2016-05-06
Also published as: DE112015004962B4; DE112015004962T5

Abstract

The objective of the present invention is to provide a terminal metal piece (1) requiring less terminal insertion force than in prior art. The terminal metal piece (1) has a base material (2) comprising a metal material, and a plating coat (3) covering the surface of the base material (2). The plating coat (3) has an outermost layer (31) containing an Sn parent phase (311) and Sn-Pd particles (312) dispersed within the Sn parent phase (311), wherein the Sn parent phase (311) and the Sn-Pd particles (312) are present on the external surface. In addition, in a state where the Sn parent phase (311) alone has been removed, the number of the Sn-Pd particles (312) present on the external surface of the plating coat (31) is 10 to 400/500 μm².

Description

Terminal fittings and connectors

The present invention relates to a terminal fitting and a connector.

As a terminal fitting used for connecting an electric circuit, a terminal fitting having a base material made of a Cu (copper) alloy and an Sn (tin) plating film covering the surface of the base material is known. The terminal fitting includes a fitting terminal that is crimped to the end of the electric wire, a board terminal that is attached to the circuit board, and the like. These terminal fittings may be used alone or may be used by being incorporated in a connector.

As a terminal material used for the terminal fitting, a terminal material in which a Ni (nickel) plating layer, a Cu plating layer, and an Sn plating layer are sequentially laminated on the surface of a Cu alloy base material is frequently used (Patent Document 1). However, since the terminal described in Patent Document 1 has a relatively soft Sn plating layer on the surface, the coefficient of friction is high, and there is a problem that the insertion force when connecting to the counterpart terminal is increased. In particular, when a terminal is incorporated in a connector and used, a multipolar structure using a plurality of terminals is often employed, and therefore the terminal insertion force tends to increase with an increase in the number of terminals.

In order to solve this problem, the inventors have proposed a technique for forming an alloy-containing layer made of Sn and Pd (palladium) and containing an Sn—Pd alloy on a base material made of copper or a copper alloy. Yes. (Patent Document 2). The plated terminal for a connector having such a configuration can reduce the terminal insertion force when fitting the mating terminal as compared with the conventional case.

JP 2003-147579 A International Publication No. 2013/168774

As a result of repeated studies, the inventors have found that the terminal insertion force can be further reduced in the terminal fitting having the alloy-containing layer containing the Sn—Pd alloy. That is, the present invention intends to provide a terminal fitting having a smaller terminal insertion force than conventional ones by controlling the number of particles made of Sn—Pd alloy.

One aspect of the present invention has a base material made of a metal material and a plating film covering the surface of the base material,
The plating film includes an Sn matrix and Sn—Pd-based particles dispersed in the Sn matrix, and has an outermost layer in which the Sn matrix and the Sn—Pd-based particles are present on the outer surface,
The terminal fitting is characterized in that the number of the Sn—Pd-based particles present on the outer surface of the plating film in a state where only the Sn matrix is removed is 10 to 400/500 μm ² .

Another aspect of the present invention is a connector having the terminal fitting of the above aspect and a housing that holds the terminal fitting.

The terminal fitting has the outermost layer containing the Sn—Pd-based particles. The number of the Sn—Pd-based particles present on the outer surface of the plating film in a state where only the Sn matrix is removed is 10 to 400/500 μm ² . By controlling the number of the Sn—Pd-based particles as described above, the terminal fitting can further reduce the coefficient of friction as compared with the conventional terminal, and thus can reduce the terminal insertion force. This is clear from Examples and Comparative Examples described later.

In addition, since the connector includes the terminal fitting of the above aspect, the insertion force when connecting to the mating connector can be reduced.

The top view of the terminal metal fitting in an Example. FIG. 2 is a partial cross-sectional view taken along line II-II in FIG. 1. The SEM image which observed the surface of the terminal metal fitting of the state which removed the Sn mother phase in an Example. The front view of the connector provided with the terminal metal fitting in an Example. FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. The top view of the terminal intermediate body in an Example. The SEM image which observed the surface of the sample C1 of the state which removed the Sn mother phase in the experiment example. The graph which shows the result of a friction test in an experiment example. The graph which plotted the maximum value of the dynamic friction coefficient in FIG. The graph which shows the result of heat resistance evaluation in an experiment example.

In the terminal fitting, the base material can be selected from various metals having conductivity. For example, Cu, Al (aluminum), Fe (iron), and alloys containing these metals can be employed as the base material. The base material can be produced by using a wire or a plate made of the above-mentioned metal as a raw material, and appropriately performing a cutting process, a punching process, a press molding process, or the like.

The plating film covering the surface of the substrate has an outermost layer containing an Sn matrix and Sn—Pd-based particles. Sn—Pd-based particles are present dispersed in the Sn matrix, and a part of the Sn—Pd-based particles is exposed on the outer surface of the plating film. Further, the Sn parent phase is exposed at the remaining part of the outer surface of the plating film. Note that a natural oxide film such as Sn may be formed on the outer surface of the outermost layer as long as it does not adversely affect the effects of reducing the terminal insertion force and improving the solder wettability.

The Sn parent phase is a phase containing Sn as a main component. Here, the main component refers to an element that is most contained in the atomic ratio among all the elements contained in the Sn matrix. In addition to Sn as a main component, the Sn matrix may contain Pd that has not been incorporated into the Sn—Pd-based particles, elements constituting the base material, elements constituting the inner layer described later, inevitable impurities, and the like. .

The Sn—Pd-based particles are particles made of an alloy that essentially contains Sn and Pd, such as PdSn ₄ . In addition to Sn and Pd as essential components, the Sn—Pd-based particles can contain elements constituting the base material, elements constituting the inner layer described later, inevitable impurities, and the like.

The outermost layer can have a Pd content of less than 20 atomic% when the total of Sn and Pd is 100 atomic%. The content of Pd is preferably less than 20 atomic%, more preferably 15 atomic% or less, still more preferably 10 atomic% or less, and even more preferably, from the viewpoint of easily ensuring the stability of contact resistance. May be 7 atomic% or less. The Pd content is preferably 1 atomic% or more, more preferably 2 atomic% or more, from the viewpoint of promoting stable formation of an intermetallic compound such as PdSn ₄ that contributes to the reduction of the friction coefficient. More preferably, it may be 3 atomic% or more, and still more preferably 4 atomic% or more.

The plating film has 10 to 400 particles / 500 μm ² of Sn—Pd-based particles on the outer surface in a state where only the Sn matrix is removed. The terminal fitting having Sn—Pd-based particles within the above specific range is deformed or dug out of the Sn matrix when mated with the counterpart terminal due to the presence of Sn-Pd-based particles that are harder than the Sn matrix, or Adhesion of the counterpart terminal with the Sn plating film can be suppressed. As a result, compared with the conventional terminal, the friction coefficient at the time of fitting the other party terminal can be further reduced, and the terminal insertion force can be further reduced.

When the number of Sn—Pd particles in the above state is less than 10/500 μm ² , the effect of reducing the friction coefficient by the Sn—Pd particles is insufficient. Therefore, in order to sufficiently obtain the effect of reducing the friction coefficient, the number of Sn—Pd-based particles in the above state is 10/500 μm ² or more. From the same viewpoint, the number of Sn-Pd-based particles is preferably 100/500 [mu] m ² or more, more preferably 150/500 [mu] m ² or more.

On the other hand, when the number of Sn—Pd-based particles exceeds 400/500 μm ² , the Sn mother phase existing in the outermost layer is insufficient, so that the electrical connection with the counterpart terminal is not sufficiently formed, and the contact resistance is increased. May be incurred. Therefore, in order to sufficiently obtain the effect of reducing the contact resistance, the number of Sn—Pd-based particles in the above state is set to 400/500 μm ² or less. From the same viewpoint, the number of Sn-Pd-based particles is preferably 300/500 [mu] m ² or less, more preferably 250 pieces / 500 [mu] m ² or less, more preferably 200 or / 500 [mu] m ² or less.

As a method for removing only the Sn parent phase in the outermost layer, for example, a method of selectively etching only the Sn parent phase without eroding the Sn—Pd-based particles can be used. In this case, as the etching solution, for example, an aqueous solution in which sodium hydroxide and p-nitrophenol are dissolved in distilled water can be used.

The plating film preferably has an area occupancy of 50 to 80% of the Sn—Pd-based particles present on the outer surface from which only the Sn matrix is removed. In addition to the number of Sn—Pd-based particles, by setting the area occupancy within the specific range, the friction coefficient can be further reduced. Further, by setting the area occupancy within the specific range, it is possible to reduce contact resistance with the counterpart terminal.

The plating film may have an inner layer having a composition different from that of the outermost layer between the base material and the outermost layer. By providing the inner layer, the adhesion between the plating film and the base material is improved to suppress the occurrence of swelling and peeling, or the base metal is prevented from diffusing toward the outermost layer. Obtainable.

The composition of the inner layer can be appropriately selected according to the material of the base material and the effect to be obtained. The inner layer may be composed of only one metal layer, or may be composed of two or more metal layers having different compositions. For example, when the base material is made of Cu or Cu alloy, by forming an inner layer made of Ni (nickel) or Ni alloy, the effects such as the above-mentioned improvement in adhesion and diffusion of the base metal can be achieved. Obtainable.

The inner layer preferably has a Ni—Sn layer having a thickness of 0.4 μm or more. In this case, the presence of the Ni—Sn layer can effectively suppress the diffusion of the base metal to the outermost layer. As a result, the effect of improving heat resistance can be obtained, and for example, problems such as increase in contact resistance due to diffusion of the base metal can be suppressed. Note that the thickness of the Ni—Sn layer is the average thickness of the Ni—Sn layer observed in one field of view when the cross section of the plating film is observed at a magnification of 2000 using an electron microscope.

The terminal fitting can be configured as a fitting-type terminal having a known shape, a terminal for a board, or the like. The fitting type terminal has an electrical contact portion that contacts the counterpart terminal and a barrel portion that crimps the electric wire. In the case where the terminal fitting is configured as a fitting-type terminal, an effect of reducing the terminal insertion force due to the plating film can be obtained as long as the plating film is provided at least in the electrical contact portion. Moreover, in the terminal pair of the fitting type terminal composed of the male terminal and the female terminal, if at least one of the terminal fittings has the plating film, the effect of reducing the terminal insertion force can be achieved. If it is the said terminal metal fitting, terminal insertion force can be reduced more.

When the terminal fitting is configured as a board terminal, it may be configured to be used by being connected to the circuit board while being held in the housing, or may be used by being directly connected to the circuit board. It may be configured. In the former case, since a plurality of terminal fittings are usually held in the housing, it is easy to suppress an increase in insertion force accompanying an increase in the number of terminals when mating with the mating connector. Therefore, the above-described effect of reducing the insertion force can be sufficiently exhibited.

The terminal fitting configured as a board terminal includes a terminal connection part electrically connected to the counterpart terminal, a board connection part electrically connected to the circuit board, and the terminal connection part and the board connection part. It is only necessary to have intervening portions that are present in between so that at least the terminal connection portion and the substrate connection portion are covered with the plating film.

The substrate terminal is usually manufactured by pressing a plate material and punching it into the shape of the terminal. Therefore, when using a plate material that has been plated in advance, the base material is exposed on the fracture surface formed by pressing. Thus, the base material exposed on the fracture surface may cause a decrease in solder wettability, and as a result, there is a risk that connection reliability when connecting the board connecting portion and the circuit board by solder bonding may be reduced. On the other hand, since the said terminal metal fitting can form the said plating film after press work, the fall of the solder wettability by exposure of a base material can be avoided.

Thus, the plated coating has good solder wettability and can reduce the friction coefficient during sliding due to the presence of the Sn—Pd-based particles. Therefore, by providing the plating film on both the terminal connection part and the board connection part, the connection reliability when the terminal fitting is connected to the circuit board by solder bonding can be further increased. Moreover, the plating film of the same material can be provided in both the terminal connection portion and the substrate connection portion, and it is not necessary to perform separate plating treatment on both. Therefore, an increase in cost due to an increase in plating processing work can be suppressed. The interposition part may be covered with the plating film or may not be covered with the plating film.

The board connecting part may have a press-fit part that is press-fitted into a through hole of the circuit board and forms an electrical connection with the circuit board through a conductive part provided in the through hole. Good. That is, the terminal fitting may be configured as a press-fit terminal, and the press-fit portion may be covered with the plating film. The press-fit terminal is configured to press-fit the press-fit portion into the through hole, thereby bringing the press-fit portion and the conductive portion into elastic contact to form an electrical connection. By providing the plating film in the press-fit portion, the friction coefficient when press-fitting into the through hole can be reduced, and the plating film can be prevented from being scraped or peeled off in the press-fit portion. Thereby, a favorable electrical connection can be formed with the circuit board.

Further, the connector can be configured to include a plurality of the terminal fittings. As described above, since the terminal fitting has a low coefficient of friction due to the presence of the plating film, it is possible to effectively reduce the fitting force that increases as the number of terminals increases. Therefore, in this case, the mating connector can be fitted with a low fitting force.

(Example)
Examples of the terminal fitting will be described with reference to the drawings. As shown in FIGS. 1 and 2, the terminal fitting 1 includes a base material 2 made of a metal material and a plating film 3 that covers the surface of the base material 2. As shown in FIG. 2, the plating film 3 includes Sn matrix 311 and Sn—Pd-based particles 312 dispersed in the Sn matrix 311, and Sn matrix 311 and Sn—Pd-based particles 312 are present on the outer surface. It has an outermost layer 31 present. Further, the number of Sn—Pd-based particles 312 (see FIG. 3) present on the outer surface of the plating film 3 in a state where only the Sn matrix 311 is removed is 10 to 400 particles / 500 μm ² .

As shown in FIGS. 1, 4, and 5, the terminal fitting 1 includes a terminal connection part 11 that is electrically connected to a counterpart terminal (not shown) and a board connection part 12 that is electrically connected to a circuit board 5. And an intervening portion 13 which is present between the terminal connecting portion 11 and the substrate connecting portion 12 is integrally provided. At least the entire surfaces of the terminal connection portion 11 and the substrate connection portion 12 are covered with the plating film 3.

Also, the terminal fitting 1 of this example is configured as a press-fit terminal. That is, as shown in FIGS. 1 and 5, the board connecting portion 12 is press-fitted into the through hole 51 of the circuit board 5 and is electrically connected to the circuit board 5 through the conductive portion 52 provided in the through hole 51. A press-fit portion 121 that forms a mechanical connection. Hereinafter, a more detailed configuration of the terminal fitting 1 will be described together with a manufacturing method.

In this example, first, a strip material made of a Cu alloy was pressed to produce a terminal intermediate 10 shown in FIG. In the terminal intermediate body 10, a plurality of terminal portions 101 having a rod shape are arranged in parallel with each other, and adjacent terminal portions 101 are connected via a carrier portion 102. As will be described later, the terminal portion 101 forms a press-fit portion 121 and is plated from the carrier portion 102 after the plating process to perform the terminal fitting 1.

Next, the entire surface of the terminal intermediate 10 was subjected to electroplating, and a Ni plating film, a Pd plating film, and a Sn plating film were sequentially laminated on the surface. The thicknesses of the Ni plating film, the Pd plating film, and the Sn plating film can be appropriately selected within the range of 0.5 to 2 μm, 0.01 to 0.1 μm, and 0.5 to 3 μm, respectively. Moreover, the conditions of these electroplating processes can be suitably selected from conventionally well-known conditions. In this example, the thicknesses of the Ni plating film, the Pd plating film, and the Sn plating film were 1 μm, 0.02 μm, and 1 μm, respectively.

After the electroplating treatment, the terminal intermediate 10 was heated and reflowed to form the plating film 3. The heating temperature in the reflow treatment can be appropriately selected within the range of 230 to 400 ° C. In this example, the terminal intermediate 10 was heated at a temperature of 350 ° C. to reflow Ni, Sn, and Pd. Thereby, as shown in FIG. 2, a plating film 3 composed of the inner layer 32 and the outermost layer 31 was formed on the substrate 2.

The inner layer 32 in this example was composed of a Ni layer 321 in contact with the substrate 2 and a Ni—Sn layer 322 in contact with the Ni layer 321. The Ni—Sn layer 322 is a layer formed by alloying a part of the Ni plating film and a part of the Sn plating film. The thicknesses of the Ni layer 321 and the Ni—Sn layer 322 were 0.8 μm and 0.58 μm, respectively.

The outermost layer 31 includes Sn matrix 311 and Sn—Pd-based particles 312 dispersed in the Sn matrix 311, and both the Sn matrix 311 and the Sn—Pd-based particles 312 are exposed on the outer surface. It was. The thickness of the outermost layer 31 was 0.7 μm.

After performing the above reflow process, the terminal intermediate body 10 was pressed to form the terminal connection portion 11 and the substrate connection portion 12 in each terminal portion 101. Then, the terminal part 101 was cut off from the carrier part 102 by punching, and the terminal fitting 1 was obtained.

The terminal fitting 1 of this example obtained by the above has the plating film 3 in the whole surface of the terminal connection part 11 and the board | substrate connection part 12. FIG. Furthermore, in this example, the plating film 3 is also formed on almost the entire surface of the interposition part 13. In addition, although the interposition part 13 has the fracture surface which the base material 2 exposed in the part from which the carrier part 102 was cut | disconnected, the exposure of the base material 2 in the interposition part 13 is a connection in terminal insertion force or solder joining It does not adversely affect reliability.

FIG. 3 shows an example of an SEM (scanning electron microscope) image of the surface of the terminal fitting 1 with the Sn matrix 311 removed by etching. As can be seen from FIG. 3, Sn—Pd-based particles 312 having a substantially rectangular parallelepiped shape were dispersed on the surface from which the Sn mother phase 311 had been removed. In addition, Ni—Sn layers 322 exposed by the removal of the Sn matrix 311 were observed between the Sn—Pd-based particles 312.

Based on the obtained SEM image, the number of Sn—Pd-based particles 312 present per 500 μm ² was counted, and it was confirmed that 153 particles / 500 μm ² of Sn—Pd-based particles 312 were present. Further, binarization processing based on contrast is performed on the SEM image, and the area occupancy of the Sn—Pd-based particles 312 is obtained from the obtained binarized image. As a result, the area occupancy of the Sn—Pd-based particles 312 is 65%. The threshold value of contrast in the binarization process was set so that the contour of the Sn—Pd-based particle 312 in the binarized image substantially coincided with the contour of the Sn—Pd-based particle 312 in the SEM image.

As shown in FIGS. 4 and 5, the terminal fitting 1 of this example is configured to be applicable to a connector 4 mounted on an automobile. The connector 4 includes a plurality of terminal fittings 1 and a housing 41 that holds the terminal fittings 1. The terminal fitting 1 is bent in an “L” shape while being held by the housing 41.

The housing 41 is made of synthetic resin, and a hood portion 413 that accommodates a mating connector (not shown) at the time of fitting is formed on the front side thereof, and a back wall 412 is integrally formed behind the hood portion 413. . The terminal fitting 1 is held by the housing 41 by being press-fitted from the terminal connection portion 11 side into a terminal press-fitting hole 411 formed in the back wall 412 of the housing 41.

As shown in FIG. 1, the terminal connection portion 11 of this example is formed in a tab shape, and is inserted into a cylindrical fitting portion of the counterpart terminal to form an electrical connection. The interposition part 13 is formed in a state in which a pair of retaining parts 131 and a pair of positioning parts 132 protrude in the width direction at the end part on the terminal connection part 11 side. The retaining portion 131 has a tapered edge near the tip, so that the terminal fitting 1 can be press-fitted into the terminal press-fitting hole 411 from the terminal connecting portion 11 side, and the opposite edge stands up and is prevented from coming off. The In addition, the positioning portion 132 has a sharp edge near the tip and is engaged with the edge of the terminal press-fitting hole 411 when the press-fitting is performed, so that the terminal fitting 1 is positioned. Further, the interposition part 13 is bent in an “L” shape after being locked in the terminal press-fitting hole 411.

Further, a press-fit portion 121 is formed in the substrate connecting portion 12 of this example. The press-fit part 121 is formed between a pair of contact pieces 122 that are bulged and formed in a substantially arc shape and whose outer side surfaces are in contact with the conductive part 52 of the through-hole 51, and the contact piece 122. It has a thin-walled portion 123 that can be plastically deformed, and its tip is tapered. The maximum diameter dimension of the press-fit portion 121 is larger than the inner diameter of the conductive portion 52 in the through hole 51. The press fit portion 121 is pressed into the through hole 51 and electrically connected to the conductive portion 52 by being compressed in the radial direction while the thin portion 123 is compressed and deformed. A pair of jig abutting portions 124 for contacting a press-fitting jig (not shown) when press-fitting the press-fit part 121 into the through hole 51 are provided in the width direction on the base end side of the press-fit part 121. It is formed in an overhanging state.

Next, the effect of the terminal fitting 1 of this example will be described.

The terminal fitting 1 has the outermost layer 31 containing Sn—Pd-based particles 312. In the state where only the Sn matrix 311 is removed, the number of Sn—Pd-based particles 312 present on the outer surface of the plating film 3 is 10 to 400/500 μm ² . Therefore, the terminal fitting 1 can further reduce the friction coefficient as compared with the conventional terminal, and thus can reduce the terminal insertion force. Moreover, since the connector 4 is provided with the terminal metal fitting 1 with a small friction coefficient, the insertion force at the time of connecting to a counterpart connector can be reduced.

The terminal fitting 1 is provided between the terminal connection part 11 electrically connected to the counterpart terminal, the board connection part 12 electrically connected to the circuit board 5, and the terminal connection part 11 and the board connection part 12. The intervening portion 13 is integrally provided, and at least the terminal connection portion 11 and the substrate connection portion 12 are covered with the plating film 3. Furthermore, the board connecting part 12 is press-fitted into the through hole 51 of the circuit board 5, and a press fit part 121 that forms an electrical connection with the circuit board 5 through the conductive part 52 provided in the through hole 51. Have. Therefore, the friction coefficient when press-fitting the press-fit part 121 into the through hole 51 can be reduced, and the plating film 3 can be prevented from being scraped or peeled off at the press-fit part 121. Thereby, a favorable electrical connection can be formed with the circuit board 5.

(Experimental example)
In this example, the friction coefficient of the terminal fitting 1 in the example is measured. In this example, a Cu alloy sheet was used as the base material 2, and a plating film 3 was formed on the surface by the same method as in the example to prepare a sample E1. Further, in the method of the example, the sample E2 was produced by changing the heating temperature in the reflow process to 320 ° C.

Furthermore, for comparison with samples E1 and E2, two types of comparative samples, sample C1 and sample C2, were prepared. Sample C1 is a sample produced by the same method as in the example except that the heating temperature in the reflow process was changed to 300 ° C. Sample C2 corresponds to a conventional Sn reflow plating material prepared by sequentially forming a Ni plating film having a thickness of 1 μm and a Sn plating film having a thickness of 1 μm on the surface of the Cu alloy plate material, and then performing a reflow treatment. It is a sample.

The outermost layer 31 made of the Sn matrix 311 and the Sn—Pd-based particles 312 was formed on the surfaces of the sample E2 and the sample C1 in the same manner as the sample E1. FIG. 7 shows an example of a surface SEM image of the sample C1 in a state where only the Sn parent phase 311 is removed by etching. As is known from FIG. 7, the inner layer 32 in the sample C1 was covered with densely formed Sn—Pd-based particles 312.

When the number of Sn—Pd-based particles 312 present per 500 μm ² was counted based on the SEM image (not shown) of the sample E2, it was found that 203/500 μm ² Sn-Pd-based particles 312 were present. confirmed. Further, binarization processing based on contrast is performed on the SEM image, and the area occupancy of the Sn—Pd-based particles 312 is obtained from the obtained binarized image. As a result, the area of the Sn—Pd-based particles 312 in the sample E2 is obtained. The occupation ratio was 75%. The thickness of the Ni—Sn layer in sample E2 was 0.45 μm.

When the number of Sn—Pd-based particles 312 present per 500 μm ² was counted based on the SEM image of the sample C1, it was confirmed that 466 particles / 500 μm ² of Sn—Pd-based particles 312 were present. Also, binarization processing based on contrast is performed on the SEM image, and the area occupancy of the Sn—Pd-based particles 312 is obtained from the obtained binarized image. As a result, the area of the Sn—Pd-based particles 312 in the sample C1 is obtained. The occupation ratio was 87%. The thickness of the Ni—Sn layer in sample C1 was 0.32 μm.

In the sample C2, since the Pd plating film was not provided when the terminal intermediate 10 was subjected to the electroplating process, the Sn—Pd-based particles 312 were not formed after the reflow process. Note that the thickness of the Ni—Sn layer in Sample C2 was 0.24 μm.

<Friction test>
Using the obtained four types of samples, a friction test was performed according to the following procedure. First, a part of the sample E1 was cut out, and the obtained plate-like material was pressed to produce a mating member having a hemispherical embossed portion with a radius of 1 mm. Next, the hemispherical embossed part of the mating member was brought into contact with each sample, and a load of 3N was applied between them. Then, while maintaining this load, the hemispherical embossed portion was moved relative to the sample at a speed of 6 mm / second, and the dynamic friction coefficient of the sample was measured.

8 and 9 show the measurement results of the friction coefficients of the samples E1, E2, C1, and C2. In addition, the vertical axis | shaft of FIG. 8 is a friction coefficient, and a horizontal axis is the moving distance of a hemispherical embossing part. 9 is the maximum value of the dynamic friction coefficient of each sample in FIG. 8, and the horizontal axis is the number of Sn—Pd-based particles 312.

As is known from FIGS. 8 and 9, the samples E1 and E2 have a lower friction coefficient than the samples C1 and C2, and the friction coefficient of the sample E1 is the highest among the four types of samples. I can understand it is low. As can be seen from FIG. 9, when the sample C1 is used as a reference, the sample E1 can reduce the maximum friction coefficient by about 45%, and the sample E2 can reduce the maximum friction coefficient by about 35%. it can.

In the samples E1 and E2, the Sn matrix 311 was removed, and then the number of Sn—Pd-based particles 312 and the area occupation ratio of the Sn—Pd-based particles 312 included in the outermost layer 31 of the plating film 3 were within the above specified range. Therefore, it is considered that the friction coefficient could be reduced as compared with the samples C1 and C2.

That is, for example, comparing FIG. 3 and FIG. 7, the Sn—Pd-based particles 312 included in the sample E1 have a larger particle size than the Sn—Pd-based particles 312 included in the sample C1, and The distance between adjacent Sn—Pd-based particles 312 tends to be relatively long. Therefore, it can be estimated that the proportion of the Sn—Pd-based particles 312 included in the sample E1 is in contact with the inner layer 32 (FIG. 2, reference numeral 312a). Therefore, in the sample E1, it is considered that the contact load applied when fitting with the counterpart terminal or the like is easily transmitted to the base material 2 through the Sn—Pd-based particles 312 and the inner layer 32. As a result of the above, it is considered that the sample E1 can suppress deformation and wear of the outermost layer 31, and thus can reduce the coefficient of friction. Further, it is considered that the friction coefficient of the sample E2 can be reduced for the same reason as the sample E1.

On the other hand, when the number of Sn—Pd-based particles 312 is excessively large as in the sample C1, a large number of fine Sn—Pd-based particles 312 are formed, so that the inner layer 32 is compared with the samples E1 and E2. It is considered that the ratio of the Sn—Pd-based particles 312b (see FIG. 2) not in contact increases. Such Sn—Pd-based particles 312b have a soft Sn matrix 311 between the base material 2 and, therefore, have an effect of suppressing deformation and wear of the Sn matrix 311 when a contact load is applied. small. Therefore, the sample C1 is considered to have a higher friction coefficient than the samples E1 and E2.

As described above, it can be understood that the Sn—Pd-based particles 312 tend to have a smaller particle size as the number contained in the outermost layer increases. Therefore, by controlling the number of Sn—Pd-based particles 312 in the specific range, it is possible to form Sn-Pd-based particles 312 having an appropriate size, and as a result, an effect of reducing the friction coefficient is obtained. It is considered possible.

The method for controlling the number of Sn—Pd-based particles 312 is not necessarily clear at the present time, but when the heating temperature in the reflow process is increased, the particle size of the Sn—Pd-based particles 312 increases, and the Sn contained in the outermost layer. It has been confirmed that the number of —Pd-based particles 312 can be easily controlled within the specific range. Therefore, in order to control the number of Sn—Pd-based particles 312 within the specific range, it is preferable to increase the heating temperature in the reflow process. Specifically, the reflow treatment is preferably performed at 290 to 400 ° C.

<Heat resistance evaluation>
Using the four types of samples obtained as described above, a heat resistance test was performed according to the following procedure. First, the contact resistance in a state where the sample was in contact with the gold probe was measured. The sample was then heated at a temperature of 120 ° C. for 120 hours. After the heating was completed, the sample was cooled to room temperature, and the contact resistance in a state where the sample was in contact with the gold probe was measured.

Fig. 10 shows the results of heat resistance evaluation. In addition, the vertical axis | shaft of FIG. 10 is the raise (m (ohm)) of contact resistance which deducted the value of the contact resistance measured before the heating from the value of the contact resistance measured after the heating. Further, the horizontal axis of FIG. 10 represents the thickness (μm) of the Ni—Sn layer of each sample.

As can be seen from FIG. 10, sample E1 and sample E2 had a smaller increase in contact resistance than samples C1 and C2, and were able to suppress an increase in contact resistance. Thus, by forming a plating film including a Ni—Sn layer having a thickness of 0.4 μm or more on the substrate, the heat resistance of the obtained terminal fitting can be further improved.

As mentioned above, although the Example of this invention was described in detail, this invention is not limited to the said Example, A various change is possible within the range which does not impair the meaning of this invention.

For example, the terminal fitting 1 may be directly mounted on the circuit board 5 without being held by the housing 41 of the connector 4. Moreover, the board | substrate connection part 12 in the terminal metal fitting 1 may be exhibiting the pin shape so that solder joining can be performed. Moreover, the terminal metal fitting 1 may be comprised as fitting type terminals, such as a male type terminal and a female type terminal.

Claims

Having a base material made of a metal material and a plating film covering the surface of the base material;
The plating film includes a Sn matrix and Sn—Pd-based particles dispersed in the Sn matrix, and has an outermost layer in which the Sn matrix and the Sn—Pd-based particles are present on the outer surface. ,
A terminal fitting, wherein the number of the Sn—Pd-based particles present on the outer surface of the plating film in a state where only the Sn matrix is removed is 10 to 400/500 μm 2 .
2. The terminal fitting according to claim 1, wherein the area occupancy of the Sn—Pd-based particles existing on the outer surface from which only the Sn matrix is removed is 50 to 80%.
The plating film has an inner layer having a composition different from that of the outermost layer between the substrate and the outermost layer, and the inner layer has a Ni—Sn layer having a thickness of 0.4 μm or more. The terminal fitting according to claim 1, wherein the terminal fitting is provided.
The terminal fitting integrally includes a terminal connection part electrically connected to the counterpart terminal, a board connection part electrically connected to the circuit board, and an intervening part existing between the terminal connection part and the board connection part. The terminal fitting according to any one of claims 1 to 3, wherein at least the terminal connection portion and the substrate connection portion are covered with the plating film.
The board connection part has a press-fit part that is press-fitted into a through hole of the circuit board and forms an electrical connection with the circuit board through a conductive part provided in the through hole. The terminal fitting according to claim 4.
A connector comprising: the terminal fitting according to any one of claims 1 to 5; and a housing for holding the terminal fitting.