JP2020111796A - Surface-treatment metallic material, production method of surface-treatment metallic material, and electronic component - Google Patents

Abstract

To provide a surface-treatment metallic material that has a uniformly formed surface-treatment layer.SOLUTION: A surface-treatment metallic material comprises: a base material; a lower layer composed of nickel, which is formed on the base material; a middle layer composed of a nickel-tin alloy, which is formed on the lower layer; and an upper layer composed of a silver-tin alloy, which is formed on the middle layer. Tin concentration variation inside the silver-tin alloy layer based on a depth direction analysis of a cross section EDS of the upper layer is within 3 mass%, and the average crystal grain diameter of the upper layer in the plane direction is between 0.001 μm and 0.5 μm.SELECTED DRAWING: Figure 3

Description

The present invention relates to a surface-treated metal material, a method for manufacturing a surface-treated metal material, and an electronic component.

Generally, copper or copper alloy is used as a base material for electronic parts such as connectors and terminals used in various electronic devices such as automobiles, home appliances, and office automation equipment, and these are rust-preventive, corrosion resistant, and electrical characteristic improved. The plating process is performed for the purpose of improving the function. There are various types of plating such as Au, Ag, Cu, Sn, Ni, solder and Pd, but the Sn plated material plated with Sn or Sn alloy is particularly cost effective, contact reliable and solderable. It is widely used for connectors, terminals, switches, and outer lead parts of lead frames.

The Sn-based plating has a problem that the contact resistance increases or the solderability deteriorates in a high temperature environment. As a method of avoiding this problem, there is a method of increasing the thickness of Sn-based plating, but this method causes a new problem that the insertion force of terminals and connectors described later increases.

In recent years, the number of pins of the connector has increased, and the increase in connector insertion force due to this has also become a problem. Since the assembly work of a connector of an automobile or the like often depends on human hands, the increase of the insertion force puts a heavy burden on the operator's hand. Therefore, it is desired to reduce the insertion force of the connector. If the number of cores of the connector is significantly increased due to large friction at the time of mating, a strong insertion/removal force is required.

In response to these problems, as a result of earnest research by the present inventors, for example, in Patent Document 1, a lower layer, a middle layer and an upper layer are sequentially provided on a substrate, and a predetermined metal is used for the lower layer, the middle layer and the upper layer, and With a predetermined thickness and composition, a metal material for electronic parts having low whisker properties, low adhesive wear and high durability can be produced.

Japanese Patent No. 5275504

By the way, as described above, various plating layers are formed on the surface of the base material with a predetermined thickness to improve the performance as an electronic component material. It turns out that there is room. This may promote alloying by subjecting a certain metal to a melting treatment in the manufacturing method (see, for example, paragraph 0074 of Patent Document 1), but the upper layer formed at that time has a nonuniform concentration fluctuation. It was found that there was a case where a layer was formed, and as a result, there was a variation in the characteristics within the layer, and it was found that there was a large variation in the measured values.

Then, this invention is made|formed in order to solve the said subject, and provides the surface-treated metal material which has the surface-treated layer formed uniformly.

As a result of intensive studies, the present inventors have provided a lower layer on a substrate, an alloy coating layer containing components of an intermediate layer and an upper layer, and by controlling the concentration fluctuation of the coating in the upper layer to a certain amount or less, sliding It has been found that the variation in characteristics can be improved over the conventional one. It was also found that the sliding characteristics can be improved by controlling the average crystal grain size of the upper layer in the plane direction within a predetermined range. Further, the intermediate layer can be formed by performing heat treatment after providing the lower layer and the alloy coating layer containing the components of the intermediate layer and the upper layer on the substrate, and as a result, different from the conventional simple alloy plating coating. The present invention has been accomplished by finding a manufacturing method that can form a layered structure and contribute to further improvement in heat resistance.

In one aspect, the present invention completed based on the above findings is a substrate, a lower layer formed on the substrate and made of nickel, and a lower layer formed on the lower layer and made of a nickel-tin alloy. An intermediate layer and an upper layer formed on the intermediate layer and composed of a silver-tin alloy, wherein the variation in tin concentration inside the silver-tin alloy layer in the cross-sectional EDS depth direction analysis of the upper layer is within 3% by mass. The surface-treated metal material has an average crystal grain size in the plane direction of the upper layer of 0.001 μm or more and 0.5 μm or less.

In one embodiment of the surface-treated metal material according to the present invention, the tin concentration in the upper silver-tin alloy layer is 5% by mass or more and 25% by mass or less.

In another embodiment of the surface-treated metal material of the present invention, the thickness of the lower layer is 0.5 μm or more and 3.0 μm or less, the thickness of the middle layer is 0.01 μm or more and 0.10 μm or less, and the thickness of the upper layer is The thickness is 0.25 μm or more and 1.0 μm or less.

The present invention, in another aspect, is an electronic component comprising the surface-treated metal material of the present invention.

In still another aspect of the present invention, a step of forming a nickel layer on a base material, a step of forming a silver-tin alloy layer on the nickel layer by wet plating, and a step of forming the silver-tin alloy layer. After that, heat treatment is performed to form a lower layer made of nickel on the base material, an intermediate layer made of a nickel-tin alloy on the lower layer, and an upper layer made of a silver-tin alloy on the intermediate layer. The upper layer has a variation in tin concentration within the silver-tin alloy layer of 3 mass% or less in a cross-sectional EDS depth direction analysis, and an average crystal grain size in the plane direction of 0.001 μm or more and 0.5 μm or less. The following is the method for producing a surface-treated metal material.

In one embodiment of the method for producing a surface-treated metal material according to the present invention, the heat treatment is performed at a temperature lower than the melting point of the silver-tin alloy.

According to the present invention, it is possible to provide a surface-treated metal material having a uniformly formed surface-treated layer.

It is a cross-sectional schematic diagram of the surface treatment metal material which concerns on embodiment of this invention. It is an Ag-Sn binary system phase diagram. It is a cross-sectional observation photograph of Example 1 by TEM.

<Structure of surface-treated metal material>
Conventionally, Sn or Ag is provided on a base material of a surface-treated metal material and various plating layers are formed by heat treatment to reduce contact resistance and insertion force and improve corrosion resistance. However, the present inventors have been studying further improvement of these performances. Therefore, conventionally, line analysis was performed by observing the cross-section of the surface-treated metal material to evaluate the plated product, but attention was paid to the fact that the content of elements contained inside the surface layer (upper layer) varied. When such a phenomenon occurs, it is considered that the sliding characteristics in the upper layer fluctuate, and the insertion force varies especially when used in an insertion/removal terminal or the like. From such a point, the present inventors pay attention to the element concentration variation inside the upper layer of the surface-treated metal material, particularly the concentration variation of the tin component, and the plating constitution for suppressing the tin variation inside the layer as much as possible, and The manufacturing conditions for that have been found. Hereinafter, the surface-treated metal material according to the embodiment of the present invention will be described.

As shown in FIG. 1, in the surface-treated metal material 10 according to the embodiment, a lower layer 12 is formed on a base material 11, a middle layer 13 is formed on the lower layer 12, and an upper layer 14 is formed on the middle layer 13. ..

(Base material)
The base material 11 is not particularly limited, but for example, a metal base material such as copper and copper alloys, iron-based materials, stainless steel, titanium and titanium alloys, aluminum and aluminum alloys can be used.

(Underlayer)
The lower layer 12 is made of nickel (Ni) and can be formed to have a thickness of 0.5 μm or more and 3.0 μm or less. By forming the lower layer 12 using Ni, the hard lower layer 12 improves the thin film lubrication effect and reduces the cohesive wear, and the lower layer 12 prevents the constituent metals of the base material 11 from diffusing into the upper layer 14. Improve heat resistance and solder wettability. When the thickness of the lower layer 12 is less than 0.5 μm, the thin film lubrication effect due to the hard lower layer is reduced, the adhesive wear is increased, and the constituent metal of the base material 11 is easily diffused into the upper layer 14, resulting in heat resistance and soldering. Wettability may deteriorate. On the other hand, if the thickness of the lower layer 12 exceeds 3.0 μm, bending workability may be deteriorated. The thickness of the lower layer 12 exerts its function by controlling in the above range, but it is preferably 0.5 μm or more and 2.0 μm or less from the viewpoint of productivity and resource saving.

(Middle layer)
Middle 13 nickel - tin (Ni-Sn) alloy, which consists mainly of Ni ₃ Sn intermetallic compound _4, the thickness may be formed to 0.01μm or 0.10μm or less. Since the middle layer 13 is made of a Ni ₃ Sn ₄ alloy, it has excellent corrosion resistance to gases such as chlorine gas, sulfurous acid gas, and hydrogen sulfide gas, and prevents the constituent metals of the base material 11 from diffusing into the upper layer 14, Improve durability such as heat resistance test and suppression of solder wettability deterioration. In the present invention, since the effect of improving the slidability can be imparted by controlling the crystal grain size of the upper layer, the lower limit of the thickness of the middle layer 13 can be sufficient to achieve the effect. If the thickness of the intermediate layer 13 is less than 0.01 μm, the heat resistance may deteriorate. On the other hand, when the thickness of the intermediate layer 13 exceeds 0.10 μm, bending workability may be deteriorated. The thickness of the middle layer 13 exerts its function by controlling in the above range, but from the viewpoint of productivity and resource saving, the thickness of the middle layer 13 is preferably 0.015 μm or more and 0.08 μm or less.

(Upper layer)
The upper layer 14 is composed of a silver-tin (Ag—Sn) alloy and can be formed to have a thickness of 0.25 μm or more and 1.0 μm or less. Since the upper layer 14 is made of an Ag—Sn alloy, the corrosion resistance to gases such as chlorine gas, sulfurous acid gas and hydrogen sulfide gas becomes good, and the contact resistance decreases. When the thickness of the upper layer 14 is less than 0.25 μm, the composition of the base material 11 and the lower layer 12 is likely to diffuse to the upper layer 14 side, and the heat resistance may deteriorate. Moreover, since the upper layer 14 is worn by the fine sliding and the lower layer 12 having a high contact resistance is easily exposed, the fine sliding wear resistance is poor, and the fine sliding tends to increase the contact resistance. On the other hand, if the thickness of the upper layer 14 exceeds 1.0 μm, the thin film lubrication effect of the hard base material 11 or the lower layer 12 may be deteriorated, and the cohesive wear may be increased. In addition, mechanical durability may be deteriorated and plating scraping may easily occur. In addition, the thickness of the upper layer 14 in the present invention is in a preferable range even in a thicker range as compared with the conventional one, but this is because even if the thickness is increased due to the refinement of the crystal grain size, the lower layer 12 and the middle layer 13 are lubricated. Since the effect can be easily exhibited and the state in which the wear resistance is improved by the crystal grain refinement can be formed, it can be suitably used even in a film thickness thicker than the conventional one. The thickness of the upper layer 14 exerts its function by controlling in the above range, but it is preferably 0.3 μm or more and 0.8 μm or less from the viewpoint of productivity and resource saving.

The variation in tin concentration inside the silver-tin alloy layer in the cross-sectional EDS depth direction analysis of the upper layer 14 made of the Ag-Sn alloy layer in the present invention is within 3 mass %. The presence of the concentration fluctuation in the depth direction causes a characteristic difference in the depth direction in the upper layer 14. As a result, for example, when the surface-treated metal material 10 is used, the upper layer is gradually worn away and the characteristics change. When the tin concentration variation in the silver-tin alloy layer in the cross-sectional EDS depth direction analysis of the upper layer 14 made of the Ag—Sn alloy layer exceeds 3 mass %, a characteristic difference in the depth direction occurs in the upper layer 14. For example, the variation of the insertion force may increase with use, and the contact resistance may also vary with use. Therefore, the tin concentration variation in the silver-tin alloy layer in the cross-sectional EDS depth direction analysis of the upper layer 14 made of the Ag-Sn alloy layer is controlled within the variation range of 3 mass% or less. By eliminating the concentration fluctuation in the depth direction of the upper layer 14, it is possible to reduce the difference in the sliding characteristics between layers, and it is possible to obtain the upper layer 14 that is uniform and has excellent characteristics. Further, in order to further suppress the characteristic difference, it is preferable to control the tin concentration variation inside the silver-tin alloy layer in the cross-sectional EDS depth direction analysis of the upper layer 14 made of the Ag—Sn alloy layer within 2 mass %.

The average crystal grain size in the plane direction of the upper layer 14 in the present invention is 0.001 μm or more and 0.5 μm or less. By controlling the average crystal grain size in the plane direction of the upper layer 14 to be 0.001 μm or more and 0.5 μm or less, the effect of improving the wear resistance in refining the crystal grains is enhanced, and the sliding characteristics are further improved. By improving the sliding characteristics, it is possible to provide an electronic component having excellent slidability when used in, for example, a connector or a press-fit terminal. If the average crystal grain size is less than 0.001 μm, it is not realistic, and if it is 0.5 μm or more, the sliding characteristics are deteriorated due to cohesive wear. Therefore, it is preferable to manufacture in the above range, more preferably 0.05 μm. Or more and 0.4 μm or less, and even more preferably 0.1 μm or more and 0.35 μm or less.

<Method of measuring average crystal grain size in the plane direction of the upper layer>
The method for measuring the average crystal grain size in the plane direction of the upper layer 14 is as follows. The surface-treated metal material 10 is cross-section processed by FIB, and a straight line of 3 μm is drawn in the plane direction at the center of the upper layer 14 in the film thickness direction. The value obtained by dividing the line segment when the crystal grain is completely cut by the number of completely cut crystal grains (the total number of the ends of the line segment is one) is adopted. This is because the crystal grain size in the thickness direction depends on the film thickness, and thus the crystal grain size in the present invention was found to be that the average crystal grain size in the plane direction contributes to sliding characteristics and insertability/extractability. by. The number of times of measurement is not particularly specified, but it is preferable to observe five arbitrary points and calculate the average value.

<Sn concentration in the upper Ag-Sn alloy layer>
Furthermore, the Sn concentration in the Ag—Sn alloy layer of the upper layer 14 is preferably 5% by mass or more and 25% by mass or less. When the Sn concentration in the Ag—Sn alloy layer of the upper layer 14 is less than 5% by mass, the sulfidation discoloration resistance becomes poor, while when it exceeds 25% by mass, the contact resistance may increase due to the oxidation of Sn. The Sn concentration of the Ag—Sn alloy layer formed on the upper layer 14 is preferably controlled within the above range, and more preferably 10% by mass or more and 20% by mass or less.

<Method for producing surface-treated metal material>
A method of manufacturing a surface-treated metal material according to an embodiment of the present invention includes a step of forming a nickel layer on a base material 11, a step of forming a silver-tin alloy layer on the nickel layer by wet plating, and a step of silver-tin. After forming the alloy layer, heat treatment is performed to form a lower layer 12 made of nickel on the base material 11, a middle layer 13 made of a nickel-tin alloy on the lower layer 12, and a silver-tin alloy made on the middle layer 13. Forming a top layer 14 that has been formed. It is very preferable to form the Ag—Sn alloy formed in the upper layer 14 by wet plating, because the upper layer 14 can be formed uniformly with the Ag—Sn alloy component. In addition, after the Ag—Sn alloy formed in the upper layer 14 is formed by wet plating, heat treatment is performed to form the Ag—Sn alloy layer of the upper layer 14 and the Ni—Sn alloy layer of the middle layer 13 with a desired thickness and uniform thickness. Since it can be formed with various compositions, it is very preferable as a manufacturing method. Regarding the heat treatment temperature, since recrystallization can be suppressed by performing the heat treatment at a temperature lower than the melting point of the Ag—Sn alloy, the average crystal grain size can be set to a desired value depending on the plating conditions of the upper layer 14, the heat treatment temperature, and the heat treatment time. Can be controlled. The heat treatment temperature is not particularly limited as long as it is a treatment below the melting point, but based on the Ag-Sn binary system phase diagram shown in FIG. Is more preferably 3/4 or more and 4/5 or less. As a more specific heat treatment temperature, 240 to 480°C is preferable, and 288 to 384°C is more preferable. The heat treatment time is not particularly specified, but if the time is too short, the thickness of the middle layer will be insufficient, and if it is too long, the crystal grain size of the upper layer will be large and may be 0.5 μm or more. ~120 seconds, more preferably 5~60 seconds.

After the heat treatment, a post-treatment using a phosphoric acid ester-based liquid described below may be performed. Alternatively, the heat treatment may be performed after a post-treatment using a phosphoric acid ester-based liquid described later before the heat treatment. The post-treatment (surface treatment) is an aqueous solution (phosphoric acid ester-based liquid) containing the one or more kinds of phosphoric acid ester and one or more kinds of cyclic organic compounds on the surface of the upper layer 14 of the plated material. It is desirable to do so. The phosphoric acid ester added to the phosphoric acid ester-based liquid serves as an antioxidant and a lubricant for plating. The phosphoric acid ester used in the present invention is represented by the general formulas [1] and [2]. Preferred examples of the compound represented by the general formula [1] include lauryl acid phosphoric acid monoester. Preferred examples of the compound represented by the general formula [2] include lauryl acid phosphoric acid diester.

(In the formulas [1] and [2], R ₁ and R ₂ each represent a substituted alkyl, and M represents hydrogen or an alkali metal.)

The cyclic organic compound added to the phosphoric acid ester-based liquid functions as an antioxidant for plating. The group of cyclic organic compounds used in the present invention is represented by the general formulas [3] and [4]. Preferred examples of the cyclic organic compound group represented by the general formulas [3] and [4] include, for example, mercaptobenzothiazole, Na salt of mercaptobenzothiazole, K salt of mercaptobenzothiazole, benzotriazole, 1-methyltriazole, Examples include tolyltriazole and triazine compounds.

(In the formulas [3] and [4], R ₁ represents hydrogen, alkyl, or substituted alkyl, R ₂ represents alkali metal, hydrogen, alkyl, or substituted alkyl, R ₃ represents alkali metal or hydrogen, R ₄ represents —SH, an amino group substituted with an alkyl group or an aryl group, or an alkyl-substituted imidazolylalkyl, and R ₅ and R ₆ represent —NH ₂ , —SH or —SM (M represents an alkali metal). Represents.)

<Applications of surface-treated metal materials>
The use of the surface-treated metal material according to the embodiment of the present invention is not particularly limited, but a surface-treated metal material that has excellent sliding characteristics and can utilize its characteristics is preferable. For example, a connector terminal using a surface-treated metal material for a contact portion, an FFC terminal or an FPC terminal, an electronic component used for an external connection electrode, and the like can be given. The terminals do not depend on the method of joining with the wiring side, such as crimp terminals, soldering terminals, press-fit terminals, and the like. Examples of the external connection electrode include a connection component whose tab is surface-treated and a surface-treated material for a semiconductor under bump metal. Further, a connector may be manufactured using the connector terminal thus formed, and an FFC or FPC may be manufactured using FFC terminals or FPC terminals. Further, in the surface-treated metal material according to the embodiment of the present invention, the female terminal connecting portion is provided on one side of the mounting portion to be attached to the housing, and the board connecting portion is provided on the other side, and the board connecting portion is formed on the board. It may be used as a press-fitting type terminal that is press-fitted into the through hole and attached to the substrate. In the connector, both the male terminal and the female terminal may be the surface-treated metal material according to the embodiment of the present invention, or only one of the male terminal and the female terminal may be used. By using the surface-treated metal material according to the embodiment of the present invention for both the male terminal and the female terminal, the low mating/unmating property is further improved. Furthermore, it can be suitably used for sliding contacts that require reciprocal sliding properties.

Hereinafter, both Examples and Comparative Examples of the present invention will be shown, but these are provided for better understanding of the present invention and are not intended to limit the present invention.

<Production of surface-treated metal material>
As Examples 1 to 19 and Comparative Examples 1 and 2, Ni plating, Ag-Sn alloy plating, and further on the surface of the base material (width 20 mm, length 80 mm, thickness 0.64 mm) under the following conditions: The surface treatment was performed in the order of heat treatment and phosphoric ester solution treatment.
As Comparative Example 3, after the Ni plating and the Ag—Sn alloy plating were formed on the surface of the substrate in the same manner as in Example 1, the phosphoric acid ester-based liquid treatment was similarly performed without heat treatment.
As Conventional Example 1, of the above conditions, surface treatment was performed in the order of Ag plating and Sn plating instead of Ag-Sn alloy plating after Ni plating. As Conventional Example 2, of the conditions of Conventional Example 1, Sn plating was not applied, only Ag plating was performed, and heat treatment was omitted to perform surface treatment.
Table 1 shows the plating thickness and heat treatment conditions of each example, conventional example, and comparative example.

(Ni plating conditions)
Surface treatment method: Electroplating plating solution: Ni sulfamate (150 g/l) + boric acid (30 g/l)
Plating temperature: 55℃
Current density: 0.5-4 A/dm ²

(Ag-Sn plating conditions)-Applicable only to Examples 1 to 19 and Comparative Examples 1 to 3-
Surface treatment method: Electroplating Plating solution: Rohm and Haas Ag-Sn alloy plating solution Product name: SILVERON GT-820
Plating temperature: 50℃
Current density: 1 to 10 A/dm ²

(Ag plating conditions)-Applicable only to Conventional Examples 1 and 2-
Surface treatment method: electroplating Plating solution: Ag cyanide (10 g/l) + potassium cyanide (30 g/l)
Plating temperature: 40℃
Current density: 0.2-4 A/dm ²

(Sn plating conditions)-Applicable only to Conventional Examples 1 and 2-
Surface treatment method: electroplating Plating solution: methanesulfonic acid Sn (50 g/l) + methanesulfonic acid (200 g/l)
Plating temperature: 30℃
Current density: 5-7 A/dm ²

(Heat Treatment)-Applicable only to Examples 1 to 19, Comparative Examples 1 and 2, and Conventional Example 1-
Heat treatment was performed on the sample after plating at the temperature and the treatment time shown in Table 1. The heat treatment atmosphere was all air atmosphere.

(Phosphate ester liquid treatment)
After the heat treatment, the phosphoric acid ester type liquid treatment was performed on the plating surface using the following phosphoric acid ester species and cyclic organic compound species under the following conditions.
・Phosphoric acid ester type: lauryl acid phosphoric acid monoester (phosphoric acid monolauryl ester)
-Cyclic organic compound species: benzotriazole-Electrolysis conditions: 2 V, 5 seconds anodic electrolysis

<Evaluation>
-Measurement of thickness of lower layer The thickness of the lower layer was measured with a fluorescent X-ray film thickness meter (SEA5100 manufactured by Seiko Instruments, collimator 0.1 mmΦ).
The measurement of the thickness of the lower layer was carried out by averaging by evaluating arbitrary 10 points.

-Determination of structure [composition] of surface layer and upper layer and middle layer and thickness measurement The structure and thickness measurement of the upper layer and middle layer of the obtained sample were determined by line analysis by STEM (scanning electron microscope) analysis. The thickness corresponds to the distance obtained from the line analysis (or surface analysis). As the STEM device, JEM-2100F manufactured by JEOL Ltd. was used. The acceleration voltage of this device is 200 kV.
Further, the determination of the structures of the upper layer and the middle layer of the obtained sample and the measurement of the thickness were performed at arbitrary 10 points and averaged. The thickness of the surface layer was measured in the same manner as the thicknesses of the upper layer and the middle layer.
In Examples 1-19, Conventional Example 1, and Comparative Examples 1 and 2 are both middle was configured with Ni ₃ Sn ₄ alloy. In the upper layer, Examples 16 and 17 are Ag-Sn solid solutions, Examples 1 to 15 and 18, Comparative Examples 1 and 2 are a mixture of Ag ₁₅ Sn ₂ alloy and Ag ₃ Sn alloy, and Example 19 and Conventional Example 1 are Ag. ₃ Sn alloy, Conventional Example 2 was composed of Ag plating, and Comparative Example 3 was composed of Ag-Sn plating.

Evaluation of variation in tin concentration inside the silver-tin alloy layer in cross-sectional EDS depth direction analysis of upper layer Regarding variation in internal tin concentration, the tin concentration in the thickness direction of the TEM flakes was determined by EDS analysis in the depth direction. The measurement was carried out at intervals of 0.05 μm, and the concentration fluctuation was defined as “maximum value-minimum value” and evaluated.

Insertion force The insertion force was evaluated by performing an insertion/extraction test with a plated male terminal using a commercially available Sn reflow plated female terminal (090 type Sumitomo TS/Yazaki 090II series female terminal non-waterproof/F090-SMTS).
The measuring device used for the test is 1311NR manufactured by Aiko Engineering Co., Ltd., and the sliding distance of the male pin was 5 mm.
In the present disclosure, when the insertion force is less than 1.4 N, it is defined as an excellent insertion force and marked with “◯”, and when it is less than 1.2 N, the insertion force is further improved. It was defined as and was attached with "◎". On the other hand, in the case of 1.4 N or more, “x” is added as a definition of being impossible.

・Regarding variation in insertion force Regarding the insertion force, the variation in the measured value is read from the same device as above, and when the variation is within ±30%, it is marked as "◎", and when it is within ±40, it is regarded as good. “O” was given, and when it was within ±50%, it was marked with “Δ”, and when it was within ±50%, it was marked with “×”.

Bending workability Regarding bending workability, after bending at 90° in the direction perpendicular to the rolling bar at the same bending radius (0.64 mm) as the plate thickness, the apex was observed with a stereomicroscope. From the observation, those with small bending wrinkles were marked as "◎", those with large wrinkles but not cracked were marked as "○", and there were slight cracks but the base material was exposed. Those that were not marked were marked with a “Δ”, and those with a crack that had exposed the base material were marked with a “X”.

-Sulfidation resistance Sulfidation resistance was evaluated in the following test environment. The evaluation of sulfidation resistance is the appearance of the sample after the test that has completed the environmental test.
Hydrogen sulfide gas corrosion test Hydrogen sulfide concentration: 10ppm
Temperature: 40°C
Humidity: 80%RH
Exposure time: 96h
As a result of observation of the appearance, those that did not discolor at all were marked as "◎", and those that were slightly discolored but had an area of less than 5% were marked as "○" and slightly When the discoloration was 5% or more and less than 20%, the color was marked with "△", and when the color was significantly discolored or the area was 20% or more was marked with "X".

Contact resistance The contact resistance was measured by a four-terminal method (precision sliding tester CRS-G2050 type Yamazaki Seiki Laboratory) with a contact load of 1N. This is because the conventional measurement is performed at 3N, but in order to adapt to a connector or an electrical contact with a lower load, the numerical value in the measured value under a lower load is important, so in the present invention. Applies a 1N measurement. As a sample, a sample immediately after plating (initial stage) was evaluated. The number of samples was 5, and the range from the minimum value to the maximum value of each sample was adopted.
In the present disclosure, when the contact resistance is 10 mΩ or less, it is defined as excellent contact resistance and is marked with “◯”, and when it is less than 5 mΩ, it is defined as even better contact resistance. Then, “◎” was added. On the other hand, in the case of exceeding 10 mΩ, “x” is added as a definition of being impossible.

In each of Examples 1 to 19, the insertion force was small and the variation in the insertion force was well suppressed.
In Conventional Example 1 and Comparative Examples 1 and 3, the variation in the Sn concentration in the upper layer was large, and therefore the variation in the insertion force was relatively large.
In Comparative Example 2, the insertion force was relatively large due to the large average crystal grain size in the plane direction in the upper layer.
FIG. 3 shows a cross-sectional observation photograph of Example 1 by TEM.

10 Surface-treated metal material 11 Base material 12 Lower layer 13 Middle layer 14 Upper layer

Claims (6)

Base material,
A lower layer formed on the base material and made of nickel,
An intermediate layer formed on the lower layer and composed of a nickel-tin alloy,
An upper layer formed on the middle layer and composed of a silver-tin alloy,
Equipped with
The variation in tin concentration inside the silver-tin alloy layer in the cross-sectional EDS depth direction analysis of the upper layer is within 3 mass %, and the average crystal grain size in the plane direction of the upper layer is 0.001 μm or more and 0.5 μm or less. , Surface treated metal materials. The surface-treated metal material according to claim 1, wherein the tin concentration in the upper silver-tin alloy layer is 5% by mass or more and 25% by mass or less. The thickness of the lower layer is 0.5 μm or more and 3.0 μm or less, the thickness of the middle layer is 0.01 μm or more and 0.10 μm or less, and the thickness of the upper layer is 0.25 μm or more and 1.0 μm or less. The surface-treated metal material as described in 1 or 2. An electronic component comprising the surface-treated metal material according to claim 1. Forming a nickel layer on the substrate,
Forming a silver-tin alloy layer on the nickel layer by wet plating;
After forming the silver-tin alloy layer, heat treatment is performed to form a lower layer made of nickel on the base material, a middle layer made of a nickel-tin alloy on the lower layer, and a silver-tin alloy on the middle layer. Forming an upper layer composed of
Equipped with
The upper layer is
The variation in the tin concentration inside the silver-tin alloy layer in the cross-sectional EDS depth direction analysis is within 3% by mass,
A method for producing a surface-treated metal material, wherein an average crystal grain size in a plane direction is 0.001 μm or more and 0.5 μm or less. The method for producing a surface-treated metal material according to claim 5, wherein the heat treatment is performed at a temperature lower than the melting point of the silver-tin alloy.