JP7059877B2 - Terminal material for connectors and terminals for connectors - Google Patents

Description

The present invention relates to a connector terminal material and a connector terminal provided with a useful film used for connecting electrical wiring of automobiles, consumer devices, etc. in which fine sliding occurs.

Conventionally, connectors used for connecting electrical wiring of automobiles and the like are known. A contact piece provided on the female terminal is electrically connected to the vehicle-mounted connector (vehicle-mounted terminal) by contacting the male terminal inserted in the female terminal with a predetermined contact pressure. Those with a pair of terminals designed to be used are used. As such a connector (terminal), a tin-plated terminal obtained by tin-plating a copper or copper alloy plate and performing a reflow process is generally used. However, in recent years, with the increase in current and voltage of automobiles, the use of terminals plated with precious metals, which can pass a larger current and have excellent heat resistance and wear resistance, is increasing.

As plating for in-vehicle terminals that are required to have such heat resistance and wear resistance, for example, silver plating as described in Patent Document 1 is known. However, the hardness of the silver-plated layer decreases because the crystal diameter of silver increases due to heating. In order to suppress this decrease in hardness, it is conceivable to increase the silver plating film thickness, but there is a problem in terms of cost. Further, as a silver-plated terminal having improved wear resistance, as described in Patent Document 2, a silver-plated terminal in which antimony is added to a silver-plated layer is known. However, antimony is not suitable for use in a high temperature environment because it is concentrated on the outermost surface of the silver-plated layer by heating and then oxidized to increase the contact resistance.

Further, in order to prevent deterioration of wear resistance due to heating, there is also a method of alloying silver plating as in Patent Document 3, but since only a part of the plating layer is alloyed, the alloyed portion slides. When it is consumed, the decrease in wear resistance cannot be suppressed. Therefore, as in Patent Document 4, it is considered to keep the composition of the entire plating layer uniform.

Japanese Unexamined Patent Publication No. 2008-169408 Japanese Unexamined Patent Publication No. 2009-79250 JP-A-2017-79143 Japanese Patent Application Laid-Open No. 2015-183216 Patent No. 5876622 International release 2015/092978

However, in the method described in Patent Document 4, since an alkaline cyan bath in which tin ions in the liquid tend to become tetravalent is used, tin ions tend to become tin oxide. Further, since the tin ion in the bath becomes tetravalent, the precipitation rate is reduced to about 1/2, and it is difficult to stably precipitate at a constant composition ratio. In addition, since the cyanide bath contains potassium cyanide, which is a toxic substance, there is a problem that the environmental load is very high and the wastewater treatment becomes complicated. Further, in the configurations described in Patent Documents 1 and 2, since the thickness of the pure tin layer on the outermost surface is thin and the amount of pure tin is small, even if slight sliding wear occurs, the generation of tin wear powder is small. Although the increase in the resistance value can be suppressed, there is a problem that the pure tin plating layer disappears quickly due to wear and the material is exposed at an early stage. Further, in the configuration of Patent Document 3, since the copper-tin alloy layer is present in the intermediate layer, there is a concern that the resistance value may increase due to the wear and oxidation of copper.

By the way, a reflow tin plating material is often used for plating an in-vehicle terminal. In this regard, Patent Documents 5 and 6 describe that the characteristics of the reflow tin-plated material are improved by applying silver plating only to the portion of the reflow tin-plated material in which wear resistance is important.
However, in the configuration described in Patent Document 5, although the silver-plated layer is formed on the reflow material, the hardness of the silver-plated layer is lowered by heating, so that the wear resistance cannot be improved. Further, in the configuration described in Patent Document 6, there is no disclosure of a technique for laminating a good silver plating layer on the reflow tin plating layer, and even if the silver plating layer can be formed on the reflow tin plating. , As mentioned above, the wear resistance cannot be improved.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a connector terminal material, a connector terminal, and a method for manufacturing a connector terminal material, which can improve wear resistance and heat resistance.

The terminal material for a connector of the present invention has a reflow tin material including a base material made of copper or a copper alloy and a reflow tin layer coated on the surface of the base material, and is formed on a part of the surface of the reflow tin material. Is coated with a silver-tin plated layer made of a silver-tin alloy, and the silver-tin plated layer contains Ag in a range of 70 at% or more and 85 at% or less, and contains a silver-tin-based intermetallic compound as a main component, and the silver. After heating the tin-plated layer at 150 ° C. for 250 hours, the average particle size of the crystal grains of the silver-tin-plated layer measured by EBSD (Backscattered Electron Diffraction: Alloy BackScanter Diffraction) is 1 μm or less, and the silver-tin-plated layer and the above. An intermetallic compound containing NiSn ₄ as a main component is arranged between the reflow tin material.

In the present invention, Ag is contained in the range of 70 at% or more and 85 at% or less, and the silver-tin intermetallic compound is the main component, and the average particle size of the crystal grains of the silver-tin plated layer is as small as 1 μm or less. Abrasion resistance can be improved. If Ag is less than 70 at%, the contact resistance after heating is lowered, and if Ag is more than 85 at%, the particle size of the silver-tin plated layer is increased and the wear resistance is lowered. Further, since the intermetallic compound containing NiSn ₄ as a main component is arranged between the silver tin plating layer and the reflow tin material, the adhesion between the silver tin plating layer and the reflow tin material (reflow tin layer) is enhanced. It is possible to improve the peel resistance (heat resistance). Examples of the silver-tin-based intermetallic compound include Ag ₃ Sn and Ag ₄ Sn intermetallic compounds.

As a preferred embodiment of the terminal material for a connector of the present invention, the film thickness of the silver-tin plated layer is preferably 1 μm or more and 50 μm or less.

If the silver-tin plating layer is less than 1 μm, the silver-tin plating layer is too thin and the silver-tin plating layer disappears quickly due to wear, the material is exposed early, and the connection reliability (heat resistance) deteriorates. there is a possibility.

As a preferred embodiment of the terminal material for a connector of the present invention, a nickel layer made of nickel or a nickel alloy is provided between the reflow tin material and the silver tin plating layer, and the thickness of the nickel layer is 0. It is preferably 5 μm or more and 5 μm or less.

In the above embodiment, since the silver tin plating layer containing the intermetallic compound of Ag ₃ Sn and Ag ₄ Sn as the main component is formed on the nickel layer, the silver tin plating layer is surely peeled off from the reflow tin material. Can be suppressed. If the thickness of the nickel layer is less than 0.5 μm, the Cu component from the base material made of copper or a copper alloy diffuses into the silver tin plating layer under a high temperature environment, and the resistance value of the silver tin plating layer becomes high. It may become large and the heat resistance may decrease, and if it exceeds 5 μm, cracks may occur during bending.

The connector terminal of the present invention is a connector terminal made of the connector terminal material, and the silver-tin plating layer is located at a contact portion.

According to the present invention, the wear resistance and heat resistance of the connector terminal material and the connector terminal can be improved.

It is sectional drawing which shows typically the terminal material for a connector which concerns on one Embodiment of this invention. It is a TEM image of the cross section (near NiSn4 compound) of the terminal material for a connector in the said embodiment. It is sectional drawing which shows typically the terminal material for a connector which concerns on the modification of the said Embodiment. It is a SIM image of the cross section of the terminal material for a connector after heating in an Example. It is a SIM image of the cross section of the terminal material for a connector after heating in a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[Structure of terminal material for connector]
The terminal material 1 for a connector of the present embodiment has a plate-shaped base material 21 made of copper or a copper alloy and reflow tin coated on the surface of the base material 21, as schematically shown in FIG. Nickel coated on the reflow tin material 2 composed of the layer 22 and a part of the surface of the reflow tin material 2 (a portion that becomes a contact portion when the terminal material 1 for a connector is processed and becomes a terminal for a connector). Alternatively, a nickel layer 3 made of a nickel alloy and a silver-tin plated layer 4 coated on the surface of the nickel layer 3 are provided. The composition of the base material 21 is not particularly limited as long as it is made of copper or a copper alloy.

The reflow tin layer 22 is formed by coating the surface of the base material 21 with a tin layer made of tin or a tin alloy and reflowing the tin layer. Specifically, (1) an intermediate alloy layer composed of an intermetallic compound layer of copper and tin is formed on the base material 21, and a tin layer is formed on the intermediate alloy layer, (2). ) An intermediate alloy layer having a structure in which a metal-metal compound layer of copper and tin is laminated on a nickel layer having a metal-metal compound of nickel and tin is formed on the base material 21 via a nickel layer 3. , A tin layer is formed on the intermediate alloy layer, and (3) between the metals of nickel and tin on the base material 21 via a base layer for a contact characteristic film made of nickel or a nickel alloy layer. There are three types: an intermediate alloy layer made of a nickel layer having a compound is formed, and a tin layer is formed on the intermediate alloy layer. In the case of (1) as well, a base layer for a contact characteristic film made of nickel or a nickel alloy layer may be provided between the base material 21 and the intermediate alloy layer. Further, in the case of (3), the intermediate alloy layer cannot be recognized as a layer by observation with a focused ion beam device (FIB) or the like, and it is recognized that a tin layer is formed on the base layer for the contact characteristic film. May be done.

The nickel layer 3 is coated by subjecting a part of the surface of the reflow tin material 2 (reflow tin layer 22) to nickel strike plating and then plating the upper surface thereof with nickel or a nickel alloy. The nickel layer 3 has a function of suppressing the diffusion of the Cu component from the base material 21 of the reflow tin material 2 into the silver tin plating layer 4 coated on the nickel layer 3. The thickness of the nickel layer 3 is preferably 0.5 μm or more and 5 μm or less. When the thickness of the nickel layer 3 is less than 0.5 μm, the Cu component is diffused into the silver tin plating layer 4 from the base material 21 made of copper or a copper alloy under a high temperature environment, and the resistance value of the silver tin plating layer 4 is high. If it exceeds 5 μm, cracks may occur during bending. The composition of the nickel layer 3 is not particularly limited as long as it is made of nickel or a nickel alloy. Further, the nickel layer 3 is not an essential configuration, and for example, the silver tin plating layer 4 may be formed on a part of the surface of the reflow tin material 2 (reflow tin layer 22) subjected to nickel strike plating.

Since the nickel strike plating layer formed by performing nickel strike plating has an extremely thin film thickness, when the nickel layer 3 is not formed, the nickel in the nickel strike plating layer contains NiSn ₄ as a main component. The nickel strike plating layer may not remain on the reflow tin layer 22.

The silver-tin plating layer 4 is located on the outermost surface of the terminal material 1 for a connector, and is coated by plating the nickel layer 3 with silver strike plating and then plating the upper surface thereof with methanesulfonic acid as a main component. Will be done. The silver-tin plated layer 4 contains a silver-tin-based intermetallic compound (for example, an intermetallic compound of Ag ₃ Sn and Ag ₄ Sn) as a main component, and contains Ag in a range of 70 at% or more and 85 at% or less. Since it contains such an intermetallic compound, wear resistance is improved. The average grain size of the crystal grains of the silver-tin-plated layer 4 measured by EBSD after heating the silver-tin-plated layer 4 at 150 ° C. for 240 hours is 1 μm or less.

The thickness of the silver-tin plated layer 4 is preferably 1 μm or more and 50 μm or less. When the silver-tin plating layer 4 is less than 1 μm, the silver-tin plating layer 4 is too thin and the silver-tin plating layer 4 disappears quickly due to wear, and the material (nickel layer 3) is exposed early, so that the connection reliability is established. The property (heat resistance) may deteriorate.

Next, a method of manufacturing the terminal material 1 for the connector will be described. The method for manufacturing the terminal material 1 for the connector includes a pretreatment step for cleaning the surface of the reflow tin material 2, a nickel strike plating step for applying nickel strike plating to a part of the surface of the reflow tin material 2, and nickel strike plating. A nickel layer forming step of forming a nickel layer 3 on the surface of the reflowed tin material 2, a silver strike plating step of silver strike plating on the surface of the nickel layer 3, and a silver strike plating of the nickel layer 3. It comprises a silver-tin plating layer forming step of forming a silver-tin plating layer 4 on the surface.

[Pretreatment process]
First, a pretreatment for cleaning the surface of the reflow tin material 2 is performed by degreasing, pickling, or the like.

[Nickel strike plating process]
Nickel strike plating is applied to the surface of the reflow tin material 2 (reflow tin layer 22). This nickel strike plating is performed in order to form an intermetallic compound containing NiSn ₄ as a main component between the nickel layer 3 and the reflow tin material 2 to enhance their adhesion. Further, nickel strike plating can be formed by electroplating using a known wood bath or the like. Since this nickel strike plating contains a large amount of hydrogen, it is preferable to form it thin so as not to take a long time.

[Nickel layer forming process]
A nickel or nickel alloy plating is applied to a portion of the reflow tin material 2 that has been subjected to nickel strike plating to form a nickel layer 3 on the reflow tin material 2. For example, it is formed by nickel plating using a nickel plating solution consisting of nickel sulfamic acid 300 g / L, nickel chloride 30 g / L, and boric acid 30 g / L under the conditions of a bath temperature of 45 ° C. and a current density of 3 A / dm ² . Will be done. The nickel plating for forming the nickel layer 3 is not particularly limited as long as a dense nickel-based film can be obtained, and may be formed by electroplating using a known watt bath. Further, when the silver tin plating layer 4 is directly formed on the surface of the reflow tin material 2, the nickel layer forming step does not have to be performed.

[Silver strike plating process]
Silver strike plating is performed on the nickel layer 3 formed on the reflow tin material 2. This silver strike plating is performed in order to improve the adhesion between the silver tin plating layer 4 formed on the nickel layer 3 and the nickel layer 3. The composition of the plating solution for performing this silver strike plating is not particularly limited as long as it is a no-cyanide bath (a plating bath containing no cyanide such as silver cyanide, silver potassium cyanide, sodium cyanide, potassium cyanide, etc.). It is desirable to use a silver bath of methanesulfonic acid as the main component.

[Silver-tin plating layer forming process]
Then, after the silver strike plating step, silver tin plating is performed on the nickel layer 3 to form the silver tin plating layer 4. For example, it contains an organic additive containing methanesulfonic acid, tin methanesulfonic acid, silver methanesulfonic acid, and sulfur, and has a free methanesulfonic acid concentration of 40 g / L and an Ag concentration of more than 40 g / L and 90 g / L or less. It is preferable to use a silver-tin plating solution having a Sn concentration adjusted in the range of 5 to 35 g / L. This silver-tin plating solution does not contain cyanide such as silver cyanide, potassium silver cyanide, sodium cyanide, and potassium cyanide. For the tin anode, both Ag and Pt / Ti insoluble electrodes are used, the area of these is at least twice that of the cathode, and the current distribution of Ag and Pt / Ti is Ag: Pt / Ti = 4: 1. Is preferable. Further, the bath temperature is 40 ° C. to 60 ° C., the current density is 1 to 15 A / dm ² , and for example, the silver-tin plated layer 4 having a film thickness of 2.5 μm is formed.

In this way, the connector terminal material 1 having the nickel layer 3 and the silver tin plating layer 4 formed on a part of the surface of the reflow tin material 2 is pressed, and the portion used as a contact is silver tin plated. Form a connector terminal on which the layer 4 is arranged.

In the present embodiment, the silver-tin plated layer 4 contains Ag in the range of 70 at% or more and 85 at% or less, and contains a silver-tin-based intermetallic compound (for example, an intermetallic compound of Ag ₃ Sn and Ag ₄ Sn) as a main component. Since the average particle size of the crystal grains of the silver-tin plated layer 4 measured by EBSD after heating the silver-tin plated layer 4 at 150 ° C. for 250 hours is as small as 1 μm or less, wear resistance can be improved. Further, since the silver tin plating layer 4 is formed on the nickel layer 3, it is possible to prevent the silver tin plating layer 4 from peeling from the reflow tin material 2 (nickel layer 3). Further, since the silver-tin plating layer 4 is formed by using a plating solution containing methanesulfonic acid as a main component and not containing cyanide, the environmental load can be reduced. Further, since the intermetallic compound containing NiSn ₄ as a main component is arranged between the silver tin plating layer 4 and the reflow tin material 2, the silver tin plating layer 4 and the reflow tin material 2 (reflow tin layer 22) are arranged. Adhesion can be enhanced, and peeling resistance (heat resistance) can be enhanced.

The silver-tin plating layer 4 of the present embodiment has a depth position P1 of 0.3 μm from the plating surface of the silver-tin plating layer 4 in the cross section toward the nickel layer 3 after the cross-sectional processing of plating is performed by FIB. The composition of P2 at a depth of 0.3 μm from the interface with the nickel layer 3 toward the surface side of the silver-tin plated layer 4 was analyzed with an electron beam microanalyzer (EPMA), and tin (Sn) and silver were analyzed. The absolute value of the difference of (P1-P2) when the composition ratio of (Ag) is calculated by Ag / (Sn + Ag) × 100 (at%) is 5 or less. That is, since the silver-tin plating layer 4 is formed by the above-mentioned plating treatment, the compositions of the intermetallic compounds of Ag ₃ Sn and Ag ₄ Sn at the above-mentioned position P1 and the above-mentioned position P2 are substantially the same. Therefore, it is possible to provide a connector terminal material 1 having excellent wear resistance and heat resistance (connection reliability) of the silver-tin plated layer 4.

In addition, the detailed configuration is not limited to the configuration of the embodiment, and various changes can be made without departing from the spirit of the present invention. For example, in the above embodiment, the reflow tin material 2 is composed of the base material 21 and the reflow tin layer 22, but the present invention is not limited to this. FIG. 3 is a diagram schematically showing a cross section of the connector terminal material 1A according to the modified example of the above embodiment. As shown in FIG. 3, the reflow tin material 2A of the connector terminal material 1A has a nickel layer 23 between the base material 21 and the reflow tin layer 22. The nickel layer 23 suppresses the diffusion of the Cu component of the base material 21 into the reflow tin layer 22. Therefore, in this modification, the nickel layer 3 is not provided between the reflow tin material 2A and the silver tin plating layer 4. In this modification as well, since nickel strike plating is applied to a part of the surface of the reflow tin material 2A, NiSn ₄ is the main component between the reflow tin material 2A and the silver tin plating layer 4. An intermetallic compound is produced. Therefore, even in this modification, the adhesion between the silver tin plating layer 4 and the reflow tin material 2A can be improved. Further, the nickel layer 3 may be formed on a part of the surface of the reflow tin material 2A shown in the above modification, and the silver tin plating layer 4 may be formed on the upper surface of the nickel layer 3.

[First Example]
After nickel strike plating was applied to a part of the surface of the reflow tin material, a nickel layer was formed, and each sample (Examples 1 to 6) in which a silver tin plating layer was formed on the nickel layer was produced. At this time, the values shown in Table 1 show the amount of Ag (g / L), the amount of Sn (g / L) and the current density in the silver tin plating solution, and the electrolytic degreasing treatment time and the nickel strike plating time of the reflow tin material. The absolute value (%) of the composition ratio difference between the silver (Ag) at the A position and the B position in the silver tin plating layer, the Ag concentration (at%) in the silver tin plating, and the average grain of the crystal grains of the silver tin plating layer. In addition to measuring the diameter, the presence or absence of formation of an intermetall compound containing NiSn ₄ as a main component was determined, and wear resistance and heat resistance (peeling resistance) were evaluated. The reflow tin material in each sample is composed of a base material made of a copper alloy, a reflow tin layer and a nickel layer located between them, and the thickness of the base material is 0.25 mm and the thickness of the reflow tin layer is 1. The thickness of the nickel layer was set to 2 μm, the thickness of the nickel layer was set to 0.5 μm, and the thickness of the silver-tin plated layer was set to 2.5 μm.

Further, among the samples of Comparative Examples 1 to 10, the samples of Comparative Examples 1 and 2 were subjected to glossy silver plating using a cyan bath manufactured by Atotech Japan. Specifically, as in Examples 1 to 6, after performing nickel strike plating for the time shown in Table 1 and performing silver strike plating on the nickel layer of the reflow tin material having a nickel layer formed on the surface thereof. , Dipping in a silver plating bath for plating. The composition of the plating bath was a standard composition, the temperature was 25 ° C., the current density was 3 A / dm ² , and a pure silver plate was used as the anode. The film thickness of the sample of Comparative Example 1 was 2.5 μm, and the film thickness of the sample of Comparative Example 2 was 10 μm. Further, as the sample of Comparative Example 3, the reflow tin material was used as it was. Further, for the samples of Comparative Examples 4 and 5, silver plating was performed after removing the oxide film and organic deposits on the reflow tin plating having a plating thickness of 1.2 μm by degreasing or pickling. The plating bath uses Nikkei Seisei Eco-Silver Strike Liquid, and after plating at 1 A / dm ² for 10 seconds, the plating bath is washed with water, and then the plating bath is plated with Nikkei Seisei Eco-Silver at 0.5 A / dm ² . Then, a silver-plated film of 50 nm was formed. After the film was formed, it was heated at 150 ° C. for 24 hours to make the outermost surface Ag ₃ Sn. For the samples of Comparative Examples 6 to 10, similarly to Examples 1 to 6, a nickel strike plating was applied to a part of the surface of the reflow tin material, a nickel layer was formed, and silver tin plating was performed on the nickel layer. Formed a layer.

[Measurement of absolute value (%) of P1 position and P2 position in the silver-tin plated layer]
After processing the cross section of the silver tin plating layer with a convergent ion beam device (FIB), the depth position P1 of 0.3 μm from the plating surface of the silver tin plating layer in the cross section toward the nickel layer and the nickel layer The composition of P2 at a depth of 0.3 μm from the interface toward the surface side of the silver-tin plated layer was analyzed with an electron beam microanalyzer: EPMA (model number JXA-8530F) manufactured by JEOL Ltd., and tin was used. The difference of (P1-P2) when the composition ratio of (Sn) and silver (Ag) was calculated by Ag / (Sn + Ag) × 100 (at%) was taken as the absolute value (%) of the position P1 and the position P2.

[Measurement of intermetallic compounds]

[Measurement of Ag concentration (at%) in silver tin plating]
The Ag concentration during silver-tin plating was measured using an electron probe microanalyzer: EPMA (model number JXA-8530F) manufactured by JEOL Ltd. with an acceleration voltage of 10 kV and a beam diameter of φ30 μm.

[Measurement of average grain size of crystal grains in silver-tin plated layer]
For the average grain size of the crystal grains of the silver-tin plating layer, the cross section of the plating film along the growth direction of electrodeposition (thickness direction of electrolytic copper) is processed by the ion milling method, and the EBSD device (EDAX / TSL OIM) is used. Using FE-SEM (JSM-7001FA manufactured by Nippon Denshi Co., Ltd.) with Data Collection), measurement was performed with a measurement range of 25 μm × 4 μm and a measurement step of 0.02 μm, and this data was analyzed by analysis software (EDAX / TSL OIM Data). Analysis was performed using Analysis ver. 5.2), and the average crystal grain size (average grain size) was calculated with the grain boundaries as the grain boundaries between the measurement points where the orientation difference between adjacent measurement points is 15 ° or more. The average particle size was measured before heating (0 h) and after heating at 150 ° C. for 240 hours (240 h).

[Presence / absence of intermetallic compounds containing NiSn ₄ as the main component]
The presence or absence and identification of the formation of an intermetallic compound containing NiSn ₄ as a main component was observed by diluting each sample to 100 nm or less using a focused ion beam device: FIB (model number: SMI3050TB) manufactured by Seiko Instruments Co., Ltd. A sample is prepared, and this observation sample is observed with a scanning transmission electron microscope: STEM (model number: Titan G2 ChemiSTEM) manufactured by FEI at an acceleration voltage of 200 kV, and the energy dispersive X-ray analyzer attached to STEM. : Measured using EDS. At this time, the intermetallic compound containing NiSn ₄ as a main component was determined to be "A", and the compound that could not be confirmed was determined to be "B".

(Evaluation of wear resistance)
Each of the sample before heating (plating material) and the sample after heating at 150 ° C. for 500 hours (plating material) were cut into test pieces of 60 mm × 10 mm, and the flat plate sample was used as a substitute for the male terminal. A sample with a protrusion of 0.0 mm was used as a substitute for the female terminal. For the sliding test, a friction and wear tester (UMT-Tribolab) manufactured by Bruker AXS Co., Ltd. was used, and the convex surface of the female test piece was brought into contact with the horizontally installed male terminal test piece, and a load of 5N was applied. Then, the male terminal test piece is slid horizontally at a moving distance of 5 mm and a sliding speed of 1 Hz, and the wear depth after 100 times of sliding is determined by whether or not the base (nickel layer) is exposed after the sliding test. Judged. At this time, those with a wear depth of less than 2.5 μm (the base is not exposed after the sliding test) are good “A”, and those with a wear depth of 2.5 μm or more (the base is exposed after the sliding test). (What is) is not possible "B".

(Evaluation of heat resistance)
The heat-resistant peeling test is performed by the cross-cut method described in JIS K5600-5-6 before heating (initial peeling) and after heating at 150 ° C. for 1000 hours in an atmospheric heating furnace (heat-resistant peeling). The one in which the film was not peeled off was regarded as good "A", and the one in which even one square was peeled off was designated as "B".

As is clear from Tables 1 and 2, in Examples 1 to 6, the silver-tin plated layer contains Ag in the range of 70 at% or more and 85 at% or less, and contains a silver-tin-based intermetallic compound as a main component. Therefore, the average particle size of the crystal grains of the silver-tin plated layer is 1.0 μm or less before and after heating, the nickel layer is not exposed before and after heating, and the wear resistance is good. It became "A" or more. Further, in Examples 1 to 6, since the intermetallic compound containing NiSn ₄ as a main component was present, it was a good "A" in both the initial peeling and the heat-resistant peeling. On the other hand, in Comparative Examples 1 to 5, since the plating layer is composed of only Ag, only Ag ₃ Sn, or reflow tin, neither wear resistance nor heat resistance after heating at 150 ° C. for 240 hours is possible. It was "B". Further, in Comparative Example 6, since the amount of Ag in the silver-tin plated layer was as small as 65 at%, many defects could not be measured. Further, in Comparative Example 7, since the amount of Ag in the silver-tin plated layer was too large at 95 at%, the average particle size of the crystal grains of the silver-tin plated layer exceeded 1.0 μm after heating, so that the material was heated for 240 hours. Later wear resistance was not possible "B". Further, in Comparative Examples 8 to 10, since the intermetallic compound containing NiSn ₄ as a main component was not present, the peel resistance after heating for 240 hours was impossible "B", and Comparative Examples 8 and 9 were found to be "B". Even in the initial peeling, the peeling resistance was not possible and was "B".

FIG. 4 is an SEM image of Example 5 after heating at 150 ° C. for 240 hours. As shown in FIG. 4, the average particle size of the crystal grains of the silver-tin plated layer of Example 5 before heating is 1 μm or less. Therefore, in order to improve wear resistance and heat resistance, it was found that it is more preferable that the average particle size of the crystal grains of the silver-tin plated layer measured by EBSD after heating at 150 ° C. for 240 hours is 1 μm or less. rice field. Further, it was found that the peel resistance can be improved if an intermetallic compound containing NiSn ₄ as a main component is arranged between the silver tin plating layer and the reflow tin material.

[Second Example]
In this second example, a sample (Example 1) in which a silver tin plating layer was directly formed on a part of the surface of the reflow tin material was produced. At this time, the values shown in Table 3 are the amount of Ag (g / L), the amount of Sn (g / L) and the current density in the silver tin plating solution, and the electrolytic degreasing treatment time and the nickel strike plating time of the reflow tin material. The absolute value (%) of the composition ratio difference between the silver (Ag) at the A position and the B position in the silver tin plating layer, the Ag concentration (at%) in the silver tin plating, and the average particle size of the silver tin particles are measured. At the same time, the presence or absence of the formation of an intermetall compound containing NiSn ₄ as a main component was determined, and the wear resistance and heat resistance (peeling resistance) were evaluated. The reflow tin material in each sample is composed of a base material made of a copper alloy, a reflow tin layer and a nickel layer located between them, and the thickness of the base material is 0.25 mm and the thickness of the reflow tin layer is 1. The thickness of the nickel layer was set to 2 μm, the thickness of the nickel layer was set to 0.5 μm, and the thickness of the silver-tin plated layer was set to 2.5 μm.

Further, the sample of Comparative Example 1 was subjected to glossy silver plating using a cyan bath manufactured by Atotech Japan Co., Ltd. in the same manner as in Comparative Example 1 of the first embodiment, and silver plating having a film thickness of 2.5 μm was performed on the substrate. A film was formed. Further, in the sample of Comparative Example 2, after removing the oxide film and organic deposits on the reflow tin plating having a tin plating thickness of 2.5 μm by degreasing or pickling, silver plating was performed to form a silver plating film of 50 nm. bottom. After the film was formed, it was heated at 150 ° C. for 24 hours to make the outermost surface Ag ₃ Sn. Further, in the sample of Comparative Example 3, a silver tin plating layer was directly formed on a part of the surface of the reflow tin material as in Example 1. In the second embodiment as well, the measurement of the intermetallic compound in the silver-tin plated layer was carried out in the same manner as in the first embodiment, and the measurement results were obtained in Example 1 and Comparative Example 3 as Ag ₃ Sn and Ag ₄ . It was confirmed that an intermetallic compound of Sn was produced and was the main component. On the other hand, in Comparative Examples 1 and 2, it was confirmed that the intermetallic compound of Ag ₃ Sn and / or Ag ₄ Sn was not produced. Further, for the evaluation of wear resistance and heat resistance, the same means as in the first embodiment were used. The results are shown in Table 4.

As is clear from Tables 3 and 4, in Example 1, the silver-tin plated layer contains Ag in the range of 70 at% or more and 85 at% or less, and the silver-tin-based intermetallic compound is the main component. The average particle size of silver-tin plating is 1.0 μm or less before and after heating, and the reflow tin layer (Sn) of the reflow tin material is not exposed before and after heating, and wear resistance. Was good "A". Further, in Example 1, since an intermetallic compound containing NiSn ₄ as a main component was present, it was a good "A" in both the initial peeling and the heat-resistant peeling. On the other hand, in Comparative Examples 1 and 2, since the plating layer is composed of only Ag or only Ag ₃ Sn, neither wear resistance nor heat resistance after heating at 150 ° C. for 240 hours is possible "B". Met. Specifically, in Comparative Example 1, the reflow tin layer (Sn) of the reflow tin material was exposed both before and after heating, and in Comparative Example 2, the reflow tin material was exposed both before and after heating. The base material (Cu) of the above was exposed. In Comparative Example 3, since the amount of Ag in the silver-tin plated layer is as high as 95 at%, the average particle size of the crystal grains of the silver-tin plated layer exceeds 1.0 μm after heating, so that after heating for 240 hours, Abrasion resistance was not possible "B". From these facts, it was found that the wear resistance and the heat resistance (peeling resistance) can be improved even when the silver tin plating layer is directly formed on the reflow tin material.

FIG. 5 is an SEM image of Example 1 after heating at 150 ° C. for 240 hours. As shown in FIG. 5, it can be seen that the crystal grains of the silver-tin plated layer after heating are very fine.

1 1A Terminal material for connector 2 2A Reflow tin material 3 Nickel layer 4 Silver tin plating layer 21 Base material 22 Reflow tin layer 23 Nickel layer P1 Position P2 Position

Claims (4)

It has a reflow tin material having a base material made of copper or a copper alloy and a reflow tin layer coated on the surface of the base material, and a part of the surface of the reflow tin material is silver tin made of a silver tin alloy. The plating layer is coated and
The silver-tin plated layer contains Ag in a range of 70 at% or more and 85 at% or less, and contains a silver-tin-based intermetallic compound as a main component.
The average particle size of the crystal grains of the silver-tin-plated layer measured by EBSD after heating the silver-tin-plated layer at 150 ° C. for 240 hours is 1 μm or less.
A terminal material for a connector, characterized in that an intermetallic compound containing NiSn ₄ as a main component is arranged between the silver tin plating layer and the reflow tin material. The terminal material for a connector according to claim 1, wherein the silver-tin plating layer has a film thickness of 1 μm or more and 50 μm or less. The claim is characterized in that a nickel layer made of nickel or a nickel alloy is provided between the reflow tin material and the silver tin plating layer, and the thickness of the nickel layer is 0.5 μm or more and 5 μm or less. The terminal material for a connector according to 1 or 2. A connector terminal made of the terminal material according to any one of claims 1 to 3, wherein the silver-tin plated layer is located at a contact portion.

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