KR20160103510A - Tin-plated material for electronic part - Google Patents

Abstract

An objective of the present invention is to provide an Sn-plated material having a low insertion/withdrawal property and satisfactory surface gloss as a conductive spring material such as a connector or a terminal. The Sn-plated material has an Sn-plated layer wherein a reflow treatment is performed on a copper substrate or a copper alloy-based substrate. The reflow Sn-plated layer comprises an Sn layer on an upper side and a Cu-Sn alloy layer on a lower side. The thickness of the Sn-plated layer is 0.2-0.8 m. The surface roughness (Ra) of the Sn-plated material in a direction perpendicular to a rolling direction is 0.05 m or lower, and RSm is 20 m or lower. An area ratio of the Cu-Sn alloy layer exposed to the outermost surface is 5-40%, and a crystal grain size of the exposed Cu-Sn alloy layer is 3 m or lower when observed from the surface.

Description

TIN-PLATED MATERIAL FOR ELECTRONIC PART BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

 TECHNICAL FIELD The present invention relates to an Sn plating material preferable as an electrically conductive spring material for electronic parts, particularly connectors and terminals.

Copper or a copper alloy alloy (hereinafter referred to as " Sn plating material ") in which Sn plating is performed as a conductive spring material such as a terminal or a connector is used. Generally, the Sn plating material is formed by forming a Cu underlayer plating layer by an electroplating method after degreasing and pickling in a continuous plating line, forming an Sn layer by an electroplating method, and finally performing a reflow treatment Thereby melting the Sn layer.

2. Description of the Related Art In recent years, the increase in the number of circuits in electronic and electrical parts has made progress in multipolarization of connectors for supplying electrical signals to circuits. Since the Sn plating material has a gas tight (airtight) structure for adhering water and an arm at the contacts of the connector due to its ductility, the insertion force of the connector per one electrode is higher than that of the connector made of gold plating or the like. Therefore, an increase in the connector insertion force due to the multi-polarization of the connector is a problem.

For example, in a car assembly line, the work of fitting the connector is now carried out with almost manpower. When the insertion force of the connector is increased, a burden is imposed on the worker at the assembly line, which leads directly to a reduction in working efficiency. In this respect, it is strongly desired to reduce the insertion force of the Sn plating material.

In general, a detector for detecting surface defects is provided on a terminal or a connector assembly line, and the defect functions by irradiating the surface of the terminal with light and detecting the reflected light. Therefore, in order to detect defects with high precision, it is required that the terminals have high surface gloss, that is, the surface gloss of the conductive spring material is high.

A typical Sn plating material is a Sn plating material which is obtained by sequentially electroplating Cu and Sn on a copper alloy and then subjecting the Sn layer to reflow treatment to form a Cu layer, a Cu-Sn alloy layer, and a Sn layer Structure, and a high surface gloss is obtained.

As a method for reducing the insertion force of a connector, Patent Document 1 discloses a method of subjecting a Cu-Ni-Si based copper alloy in advance to roughening treatment, then subjecting Cu and Sn to electroplating, Deg.] C for 1 to 12 seconds so that the Sn-based surface layer has an average thickness of 0.4 to 1.0 mu m or less, a part of the Cu-Sn alloy layer is exposed on the outermost surface, Discloses a technique of achieving a low-sputtering property by setting the surface roughness Ra of the Cu-Sn alloy layer to 0.3 mu m or more and Rvk to 0.5 mu m or more by substitution.

In Patent Document 2, Cu and Sn are subjected to electroplating in a Cu-Ni-Si-based copper alloy in order and reflowing treatment at 240 to 360 ° C for 1 to 12 seconds in order so that a part of Cu of the Cu- And Si, whereby the surface roughness Rvk of the Cu-Sn alloy layer exceeds 0.2 m and the Cu-Sn alloy layer is exposed to the outermost surface so that the area ratio is 10 to 40%, the average thickness of the Sn-based surface layer is 0.2 To 0.6 占 퐉.

Patent Document 3 discloses a method of reducing the Cu concentration from the base material to the surface by passing the copper alloy electroplated in the order of Cu and Sn through a reflow furnace at 300 to 900 캜 for 3 to 20 seconds, Discloses a technique in which both Sn and Sn alloys are partially dispersed in a Cu-Sn alloy layer to achieve both a low-temperature sputtering and a high heat resistance.

Patent Document 4 discloses a Cu-Ni-Si-based copper alloy in which Cu and Sn are sequentially electroplated, heated to 240 to 360 ° C, held for 6 to 12 seconds, The Cu-Sn alloy layer has a kurtosis Rku of more than 3, and the Cu-Sn alloy layer is exposed to the outermost surface, and the area ratio of the Cu- 40%, and the average thickness of the Sn-based surface layer is 0.2 to 0.4 占 퐉.

Japanese Laid-Open Patent Publication No. 2014-208878 Japanese Patent Publication No. 5263435 Japanese Patent Publication No. 5355935 Japanese Laid-Open Patent Publication No. 2013-049909

As described above, in order to reduce the insertion force of the terminal and the connector, it is effective to expose a part of the Cu-Sn alloy layer to the outermost surface of the Sn plating material. However, when the Cu-Sn alloy layer is exposed to the outermost surface, the surface roughness of the Sn plating material increases, and good surface gloss can not be obtained. Therefore, it is difficult to detect surface defects in the assembly line of the terminal or the connector. As far as the inventors of the present invention know, no inventions have been found to obtain a low-profile and good surface gloss.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a Sn plating material having a low surface roughness and good surface gloss as a conductive spring material such as a connector or a terminal.

As a result of an intensive investigation by the present inventors, it has been found that it is effective to miniaturize the crystal grain size of the Cu-Sn alloy layer exposed on the outermost surface of the Sn plating material in order to obtain a low-profile and good surface gloss.

When the Cu-Sn alloy layer is exposed on the outermost surface of the Sn plating material in the reflow treatment, since the cross-sectional shape of the Cu-Sn alloy layer is dome-shaped, the Sn melted in the reflow treatment is a Cu- Fluidity occurs along the shape, surface roughness of the Sn plating material after the reflow treatment is increased, and surface gloss is deteriorated.

Therefore, by making the crystal grain size of the exposed Cu-Sn alloy layer finer, the fluidity of the Sn layer generated in the reflow treatment can be reduced, and the surface gloss can be obtained with good accuracy.

That is,

(1) A Sn plating material having a Sn plating layer subjected to a reflow treatment on a substrate of copper or a copper alloy bath, wherein the reflow Sn plating layer is composed of an upper Sn layer and a lower Cu-Sn alloy layer, Sn alloy layer has a surface roughness Ra of not more than 0.05 mu m and an RSm of not more than 20 mu m in a direction perpendicular to the rolling direction of the Sn plating material and an area ratio of the Cu-Sn alloy layer exposed on the outermost surface is 5 to 40% Wherein the exposed Cu-Sn alloy layer has a crystal grain size of 3 占 퐉 or less.

(2) The base material of a copper or copper alloy tank is coated with a Cu undercoat layer or an Ni undercoat layer or a Ni / Cu two-layer undercoat layer in which Ni and Cu are stacked in this order, and a reflow Sn plating layer 1) Sn plating material.

(3) a Sn plating material in which a Sn layer is formed on a substrate via a Cu-Sn alloy layer by forming Sn plating or Cu or Sn plating layer in this order on a substrate of copper or copper alloy tanks, Wherein the reflow treatment is carried out at a temperature of 400 to 600 占 폚 for 1 to 30 seconds while the thickness of the Cu plating layer is 0 to 0.5 占 퐉 and the thickness of the Sn plating layer is 0.5 to 1.5 占 퐉, Wherein the cooling water is sprayed at a temperature of from -90 to < RTI ID = 0.0 > 90 C < / RTI >

(4) A Ni-Cu-Sn plating layer is formed on a substrate of a copper or copper alloy bath in this order and then subjected to a reflow treatment to form a Ni- Sn alloy layer having a thickness of 0.05 to 0.5 占 퐉, a thickness of the Sn-plated layer of 0.5 to 1.5 占 퐉 Wherein the reflow treatment is carried out at a temperature of 400 to 600 ° C for 1 to 30 seconds and then a cooling water of 20 to 90 ° C is sprayed and then charged into a water bath at 20 to 90 ° C Way.

(5) An electronic part comprising the Sn plating material according to any one of (1) and (2).

The Sn plating material according to the present invention has a low insertion force at the time of joining, particularly in terminals used for automobiles and electronic parts, and the surface inspection at the time of terminal assembly can be performed with high accuracy.

1 is an explanatory diagram of a specular reflectance measurement method.
2 is an explanatory view of a method for measuring dynamic friction coefficient.
3 is an explanatory diagram of a method of machining a contact tip.
4 is an SEM reflection electron image of the Sn plating material of the present invention.

Hereinafter, one embodiment of the Sn plating material according to the present invention will be described. In the present invention, "%" means% by mass unless otherwise specified.

(1) Composition of substrate

Tough pitch copper or oxygen-free copper having a purity of 99.9% or more can be used as the copper material to be the base material of the Sn plating material. The copper alloy can be a known copper alloy depending on the required strength and conductivity. Examples of the known copper alloys include Cu-Sn-P alloys, Cu-Zn alloys, Cu-Ti alloys, Cu-Ni-Si alloys, Cu- Based alloy and the like.

(2) Sn plating layer

On the surface of the copper or copper alloy bath, a Sn plating layer subjected to a reflow treatment is formed. The Sn plating layer is plated on the surface of the substrate directly or through a base plating. The undercoating may be Cu undercoating or Ni / Cu in this order to form a Cu / Ni two-layer undercoat. The plating thickness of the Sn layer after the reflow treatment is set to 0.2 to 0.8 mu m. Preferably 0.3 to 0.7 mu m, and more preferably 0.4 to 0.6 mu m. If the plating thickness of the Sn layer is too small, the area ratio of the later Cu-Sn alloy layer is excessively large, and the surface roughness Ra in the direction perpendicular to the rolling direction of the Sn plating layer after the reflow treatment and / or RSm becomes excessively large, It does not. On the other hand, if the plating thickness of the Sn layer is excessively large, the area ratio of the later Cu-Sn alloy layer becomes excessively small and the insertion force is not reduced.

(3) Cu-Sn alloy layer

When the reflow treatment is performed after the Sn plating, the Cu of the substrate and / or the Cu underlying layer diffuses into the Sn plating layer, and the Cu-Sn alloy layer is formed below the Sn plating layer. Normally, Cu ₆ Sn ₅ and / or Cu ₃ Sn are included. However, the above-mentioned base plating component or an additive element when the base material is a copper alloy may be contained.

The Cu-Sn alloy layer exposed on the outermost surface of the Sn plating material has a crystal grain size of 3 占 퐉 or less. Preferably 2.5 mu m or less, and more preferably 2 mu m or less. If the crystal grain size becomes too large, the surface roughness Ra in the direction perpendicular to the rolling direction of the Sn-plated layer after the reflow treatment and / or RSm becomes excessively large, and good surface gloss can not be obtained. The lower limit of the crystal grain size is not particularly limited within the range in which the effect of the present invention is exhibited, but it is difficult to make the lower limit of the crystal grain size smaller than 0.1 mu m.

The area ratio of the Cu-Sn alloy layer exposed on the outermost surface of the Sn plating material is 5 to 40%. Preferably 8 to 35%, and more preferably 10 to 30%. If the area ratio is too small, the insertion force is not reduced. On the other hand, if the area ratio is excessively large, the surface roughness Ra in the direction perpendicular to the rolling direction of the Sn plating layer after the reflow treatment and / or RSm becomes excessively large, and good surface gloss can not be obtained.

(4) Surface roughness

The surface roughness Ra of the outermost surface of the Sn plating material after the reflow treatment in the direction perpendicular to the rolling direction is 0.05 mu m or less and RSm is 20 mu m or less. Preferably, Ra is 0.03 占 퐉 or less, RSm is 15 占 퐉 or less, more preferably Ra is 0.02 占 퐉 or less, and RSm is 12 占 퐉 or less. When the surface roughness Ra in the direction perpendicular to the rolling direction and / or RSm becomes excessively large, good surface gloss can not be obtained. The lower limit of the surface roughness is not particularly limited in the range in which the effects of the present invention are exhibited, but it is difficult to produce Ra less than 0.001 탆 and RSm less than 1 탆.

(5) Manufacturing method

A Sn plating material according to an embodiment of the present invention is a Sn plating material which is obtained by degreasing and pickling a surface of a copper or copper alloy tank as a base material in a continuous plating line and then forming a base plating layer by an electroplating method, And a reflow process is performed at the end to melt the Sn layer. The underlying plating layer may be omitted.

It is not necessary to perform Cu undercoating, but when Cu undercoating is performed, the thickness is set to 0.5 占 퐉 or less. Preferably 0.4 mu m or less, and more preferably 0.35 mu m or less. If the thickness is too large, the crystal grain size of the exposed Cu-Sn alloy layer becomes excessively large, and the surface roughness Ra and RSm of the Sn plating layer after the reflow treatment in the direction perpendicular to the rolling become excessively large and good surface gloss can not be obtained.

In order to improve heat resistance, Ni undercoating may be performed before Cu undercoating. In this case, the thickness of the Ni underlying plating is not particularly limited, but if the thickness is less than 0.05 탆, the effect of Ni plating is not exhibited. If the thickness exceeds 3 탆, not only the economical efficiency is deteriorated but also the bending workability is deteriorated . Therefore, the thickness of the Ni underlying plating is preferably 0.05 to 3 mu m. The thickness of the Cu undercoating after Ni plating is not particularly limited, but if the thickness is less than 0.05 占 퐉 or exceeds 0.5 占 퐉, the effect of Cu undercoating after Ni plating is not exerted. Therefore, the thickness of the Cu undercoating after Ni plating is preferably 0.05 to 0.5 mu m.

The thickness of the Sn plating is 0.5 to 1.5 占 퐉. Preferably 0.6 to 1.2 mu m, and more preferably 0.7 to 1.1 mu m. If the thickness of the Sn plating is excessively small, the thickness of the Sn layer after the reflow treatment becomes excessively small. As a result, the area ratio of the Cu-Sn alloy layer becomes excessively large and the surface roughness of the Sn plating layer after the reflow treatment, Ra and / or RSm becomes excessively large and good surface gloss can not be obtained. On the other hand, if the thickness of the Sn plating is excessively large, the thickness of the Sn layer after the reflow process becomes excessively large, and the area ratio of the Cu-Sn alloy layer becomes too small, so that the insertion force is not reduced.

The reflow treatment is performed by heating the Sn plating material at a temperature in the furnace at 400 to 600 ° C for 1 to 30 seconds, spraying cooling water of 20 to 90 ° C onto the surface of the Sn plating material, As shown in FIG.

If the heating temperature is 400 占 폚 and / or the heating time is less than 1 second, the area ratio of the Cu-Sn alloy layer exposed on the outermost surface becomes less than 5%, and the insertion force is not reduced. Conversely, when the heating temperature is 600 占 폚 and / or the heating time exceeds 30 seconds, the crystal grain size of the Cu-Sn alloy layer exposed on the outermost surface exceeds 3 占 퐉, the area ratio thereof exceeds 40% When the surface roughness Ra in the direction perpendicular to the rolling direction is 0.05 占 퐉 and / or the RSm exceeds 20 占 퐉, good surface gloss can not be obtained.

The reason for spraying the cooling water after heating is as follows. The sprayed water particles adhere to the surface of the heated plating material, the portion is quenched, and the growth of the Cu-Sn alloy layer is suppressed. On the other hand, the portion to which no water particles adhere is not quenched, and the growth of the Cu-Sn alloy layer is not suppressed. Therefore, it is possible to generate a difference in local cooling rate on the surface of the plated layer after heating, and the crystal grain size of the Cu-Sn alloy layer exposed on the surface of the plated material can be miniaturized.

Example

The following examples illustrate the invention, but the invention is not intended to be limited to the following examples.

An ingot to which each element was added so as to be a ratio (mass%) shown in Table 1 was cast with tough pitch copper as a raw material and subjected to hot rolling to a thickness of 10 mm at 900 ° C or higher, After cold rolling and heat treatment were repeated, a plate (substrate) having a thickness of 0.2 mm was finished.

Subsequently, after degreasing and pickling the surface of the substrate, a Ni plating layer and a Cu plating layer are formed in this order on the underlying plating layer by electroplating. In some cases, Ni plating and Cu plating are omitted, A Sn plating layer was formed. In case of performing Ni undercoating, electroplating was performed in a sulfuric acid bath (liquid temperature: about 50 ° C, current density: 5 A / dm 2), and the thickness of Ni undercoat was set to 0.3 μm. When Cu undercoating was performed, electroplating was performed in a sulfuric acid bath (liquid temperature: about 25 ° C, current density: 30 A / dm 2). The Sn plating was electroplated in a phenol sulfonic acid bath (liquid temperature: about 35 ° C, current density: 12 A / dm 2). The plating thicknesses of the Cu undercoating and Sn plating were adjusted by adjusting the electrodeposition time.

Next, after heating for 1 to 30 seconds in a furnace heated at 350 to 650 占 폚, cooling water at 70 占 폚 was sprayed as a mist, and then charged into a water bath at 70 占 폚. In some embodiments, the mixture was heated and then introduced into a water bath at 70 DEG C without performing a mist cooling operation.

Each Sn plating material thus obtained was evaluated for its properties.

(1) Sn plating thickness

The thickness of the Sn-plated layer was measured using a CT-1 type electrolytic film thickness meter (manufactured by Denso Corporation).

(2) Surface roughness

The surface roughness Ra and RSm of the Sn plating material in the direction perpendicular to the rolling direction were measured according to JIS B 0601 using a confocal microscope (HD100, manufactured by Lasertec Co., Ltd.).

(3) Area ratio of exposed Cu-Sn alloy layer

Using a FE-SEM (XL30SFEG manufactured by Nippon FEI Co., Ltd.), a reflection electron image with a field of view of 0.017 mm 2 was observed at a magnification of 750 times. Since the Cu-Sn alloy layer exposed on the surface becomes a dark image as compared with the Sn layer, this image is binarized to obtain the area of the Cu-Sn alloy layer to calculate the area ratio. The binarization was carried out by setting 170 out of the altitude range 255.

(4) The grain size of the Cu-Sn alloy layer exposed on the outermost surface

The reflection electron image of the Cu-Sn alloy layer exposed at a magnification of 2000 times was observed using FE-SEM (XL30SFEG manufactured by Nippon FEI Co., Ltd.). Thereafter, 10 randomly selected Cu-Sn alloy layers were obtained, and the maximum diameter of each Cu-Sn alloy layer was determined, and the average diameter of the 10 largest circles was determined as the crystal grain size of the Cu-Sn alloy layer Respectively.

(5) Surface gloss

The specular reflectance of the Sn plating material was measured using a digital gloss gloss meter (VG-1D manufactured by Nihon Densoku Kogyo K.K.). As shown in Fig. 1, the mirror reflectance of the Sn-plated material was measured by introducing light at an angle of incidence of 30 DEG from the transparent portion and detecting light reflected by the Sn plating material at an angle of 30 deg. Since the specular reflectance when receiving light directly from the transparent portion is 100%, the higher the value is, the better the surface gloss of the Sn plating material becomes.

(6) Coefficient of friction

The coefficient of dynamic friction was measured as an evaluation of the insertion force. As shown in Fig. 2, a plate sample of the Sn plating material was fixed on the sample table, and the contact was pressed against the Sn plating surface with a load W. Next, the movable table is moved in the horizontal direction, and the resistance load F acting on the contactor at this time is measured by the load cell. Then, the dynamic friction coefficient μ was calculated from μ = F / W.

W was 4.9 N, and the sliding speed of the contactor (moving speed of the sample table) was 50 mm / min. Sliding was performed in a direction parallel to the rolling direction of the plate specimen. The sliding distance was 100 mm, and the average value of F between them was obtained.

The contacts were made as shown in Fig. 3 using the same Sn plating material as the above plate sample. That is, a stainless steel sphere having a diameter of 7 mm was pressed against the sample to form a semi-spherical portion in contact with the plate sample.

Examples are shown in Tables 2 and 3. 4 is an SEM reflection electron image of the surface of the Sn plating material of Inventive Example 4; A fine Cu-Sn alloy layer is exposed on the outermost surface of the Sn plating material.

Inventive Examples 1 to 35 show that the Sn plating layer after reflow has a thickness of 0.2 to 0.8 占 퐉, the surface roughness Ra of the Sn plating material in the direction perpendicular to the rolling direction is 0.05 占 퐉 or less, the RSm is 20 占 퐉 or less, -Sn alloy layer was 5 to 40%, and the exposed Cu-Sn alloy layer had a crystal grain size of 3 mu m or less when observed from the surface. These Sn plating materials had a mirror surface reflectance of 70% or more, good surface gloss was obtained, and a coefficient of dynamic friction was as low as 0.5 or less. In other words, both the low-profile and the good surface gloss are compatible.

Comparative Example 1 is an example in which the Sn plating thickness during plating is less than 0.5 占 퐉. The Sn layer thickness after reflow was less than 0.2 占 퐉, the area ratio of the Cu-Sn alloy layer exposed on the outermost surface exceeded 40%, the Ra in the direction perpendicular to the rolling direction exceeded 0.05 占 퐉, and the specular reflectance was less than 70% .

Comparative Example 2 is an example in which the Sn plating thickness during plating exceeds 1.5 占 퐉. The Sn-layer thickness after the reflow was more than 0.8 mu m, the area ratio of the Cu-Sn alloy layer exposed to the outermost surface was 0%, that is, the Cu-Sn alloy layer was not exposed and the coefficient of dynamic friction exceeded 0.5 .

Comparative Example 3 is an example in which the thickness of the Cu undercoat layer during plating exceeds 0.5 占 퐉. The Cu-Sn alloy layer exposed on the outermost surface has a crystal grain size of more than 3 占 퐉, Ra of more than 0.05 占 퐉, RSm of more than 20 占 퐉, and a specular reflectance of less than 70%.

Comparative Example 4 is an example in which the furnace temperature of the reflow process is less than 400 ° C, and the heating time of the reflow process is less than 1 second in Comparative Example 6. The area ratio of the Cu-Sn alloy layer exposed on the outermost surface in both cases was less than 5%, and the coefficient of dynamic friction exceeded 0.5.

Comparative Example 5 is an example in which the furnace temperature of the reflow process exceeds 600 ° C and the heating time of the reflow process exceeds 30 seconds in Comparative Example 7. Sn layer thickness after reflow is less than 0.2 占 퐉, the area ratio of the Cu-Sn alloy layer exposed on the outermost surface exceeds 40%, the crystal grain size exceeds 3 占 퐉, the Ra in the direction perpendicular to the rolling direction is 0.05 占 퐉 , RSm was more than 20 占 퐉, and the specular reflectance was less than 70%.

Comparative Examples 8 to 11 are examples in which mist cooling is not performed. The area ratio of the Cu-Sn alloy layer exposed on the outermost surface is more than 5% and the coefficient of dynamic friction is 0.5 or less. However, when the crystal grain size of the Cu-Sn alloy layer exposed on the outermost surface exceeds 3 탆 , The surface roughness Ra exceeded 0.05 占 퐉, the RSm exceeded 20 占 퐉, and the specular reflectance was less than 70%. In other words, it was impossible to achieve both the low-temperature sputtering and the good surface gloss.

Claims (5)

A Sn plating material having a Sn plating layer subjected to a reflow treatment on a substrate of copper or a copper alloy tank, wherein the reflow Sn plating layer is composed of an upper Sn layer and a lower Cu-Sn alloy layer, 0.8 m, the surface roughness Ra of the Sn plating material in the direction perpendicular to the rolling direction is 0.05 占 퐉 or less, RSm is 20 占 퐉 or less and the area ratio of the Cu-Sn alloy layer exposed to the outermost surface is 5 to 40% Wherein the exposed Cu-Sn alloy layer has a crystal grain size of 3 占 퐉 or less. The method according to claim 1,
The base material of the copper or copper alloy tanks is coated with a Cu underlayer plating layer or an Ni undercoating layer or a Ni / Cu two-layer undercoat layer in which Ni and Cu are stacked in this order, and a reflow Sn plating layer thereon, Sn plating material. A Sn plating material in which a Sn layer is formed on a substrate via a Cu-Sn alloy layer is manufactured by forming Sn plating or Cu or Sn plating layer on the substrate of copper or copper alloy tanks in this order and then performing reflow treatment The reflow treatment is performed at a temperature of 400 to 600 占 폚 for 1 to 30 seconds, and then the refractory treatment is performed at a temperature of 20 to 90 占 폚 Of cooling water is sprayed, and then the mixture is introduced into a water bath at 20 to 90 占 폚. A Ni-Cu alloy layer is formed on the substrate of copper or copper alloy in this order and then subjected to a reflow treatment to form a Ni-Cu plating layer or a Ni / Cu two- Wherein the thickness of the Ni plating layer is 0.05 to 3 占 퐉, the thickness of the Cu plating layer is 0.05 to 0.5 占 퐉, the thickness of the Sn plating layer is 0.5 to 1.5 占 퐉, Wherein said reflow treatment is performed at a temperature of 400 to 600 ° C for 1 to 30 seconds, then cooling water is sprayed at 20 to 90 ° C, and then the solution is introduced into a water bath at 20 to 90 ° C. An electronic part comprising the Sn plating material according to claim 1 or 2.

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