KR20160103534A - Sn-PLATED MATERIAL FOR ELECTRONIC COMPONENT - Google Patents

Abstract

The purpose of the present invention is to provide an Sn-plated material which prevents the generation of Sn powder as a conductive spring material such as a connector or terminal, and also has good surface gloss. A reflow Sn-plated layer, as the Sn-plated material having an Sn-plated layer formed by performing a reflow process on a substrate of copper or copper alloy strip, comprises an upper Sn layer and a lower Cu-Sn alloy layer. On the uppermost surface of the Sn-plated material, there is one per 35 mm^2 in a radial Sn solidification structure. The surface roughness Ra of the rolling orthogonal direction of the outermost surface of the Sn-plated material is 0.05 um or less.

Description

Sn-PLATED MATERIAL FOR ELECTRONIC COMPONENT FOR ELECTRONIC COMPONENTS

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

A copper or copper alloy tank (hereinafter referred to as " Sn plating material ") in which Sn plating is applied as a conductive spring material such as a terminal or a connector is used. Generally, the Sn plating material is obtained by forming a Cu underlying layer by electroplating after degreasing and pickling in a continuous plating line, forming an Sn layer by electroplating, and finally reflowing the Sn layer Melting process.

When the Sn plating material is pressed to produce a connector or the like, a Sn plating material is pressed by a pad. However, since the pad contacts the surface of the Sn plating material, Sn powder is generated from the Sn plating layer of the Sn plating material, Respectively.

In general, a detector for detecting surface defects is provided on an assembly line of a connector or the like, 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 surface of the terminal has a high gloss, that is, the surface gloss of the conductive spring material is high.

With the recent miniaturization of connectors, Sn plating materials are strongly required to suppress the generation of the Sn powder and to have good surface gloss.

In relation to the problem of the Sn powder, in Patent Document 1, the Cu-Sn alloy layer is exposed on the outermost surface of the Sn plating member by controlling the frequency of the fan in the reflow process after the base alloy plating and the Sn plating are performed in the copper alloy tank, And the area ratio of the exposed Cu-Sn alloy layer is set to 0.5 to 4%, and the number of the exposed Cu-Sn alloy layer is set to 100 to 900 per 0.033 mm 2.

In Patent Document 2, Cu-Sn alloy particles having a particle diameter of 10 to 100 nm are contained in the reflowed Sn layer by cooling the copper alloy tank with base plating and Sn plating, heating in a reflow furnace, air cooling, At a number density of 50 to 1000 pieces / 占 퐉 ² .

Japanese Patent No. 5389097 Japanese Patent No. 5587935

Although the Sn plating material is effective in suppressing the generation of Sn powder, it is insufficient to meet the demand for suppressing the occurrence of Sn powder accompanying the recent miniaturization of the connector. Further, in order to carry out surface inspection with high precision, it is required to improve surface gloss.

An object of the present invention is to further improve the suppression of generation of Sn powder and to obtain good surface gloss. As far as the inventors of the present invention know, no inventions have been found which suppress the generation of Sn powder and obtain good surface gloss.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a Sn plating material which prevents generation of Sn powder as a conductive spring material of a connector or a terminal and has good surface gloss.

As a result of intensive study by the present inventors, it has been found that it is effective to improve the surface smoothness of the Sn plating material in order to suppress the generation of Sn powder. The Sn powder is generated by cutting the Sn layer when holding the Sn plating material with the pad in the press working. 1, when the surface roughness of the Sn plating material is large, the area of contact with the pad becomes small, so that the load per unit area of the contact portion between the pad and the Sn plating material becomes large, The punching amount of the Sn plating material of the pad becomes large. As a result, the amount of Sn plating material is increased and the amount of Sn powder produced is increased.

On the contrary, if the surface roughness of the Sn plating material is small, as shown in Fig. 2, the area of contact with the pad is widened, so that the load per unit area of the contact portion between the pad and the Sn plating material becomes small, The build amount becomes smaller. As a result, the amount of the Sn plating material to be cut is reduced, and the amount of the Sn powder to be generated is reduced. Also, as the surface roughness of the Sn plating material becomes smaller, the surface gloss is improved.

In order to reduce the surface roughness of the Sn plating material, a copper alloy bath in which Sn plating is performed by reflow treatment is heated, and then cooling water is sprayed on the surface of the Sn plating material (hereinafter referred to as " It is necessary to apply Sn plating method.

In general, a method of cooling a plated material heated by a reflow treatment is a method of putting the plated material into a water tank after heating, or air-cooling the plated material for several seconds, and then introducing the plated material into a water tank. In this case, since the Sn melted by the reflow heating solidifies immediately after being introduced into the water tank, the solidified structure of the Sn becomes a columnar shape as shown in Fig. Therefore, the cross-sectional shape becomes as shown in Fig. 1, and the surface roughness becomes large.

On the other hand, when the plating material heated by the reflow treatment is applied to the bath before the plating bath is cooled, water particles sprayed on the surface are adhered to the surface and cooled, so that the solidified structure form of the Sn is radial do. Therefore, the sectional shape thereof is as shown in Fig. 2, and the surface roughness is reduced.

As described above, by cooling the plating material heated by the reflow treatment and cooling it by putting it into a water bath to make the solidified structure form of Sn radial and reducing the surface roughness, generation of Sn powder can be suppressed So that good surface gloss can be obtained.

That is,

(1) A Sn plating material having a Sn plating layer subjected to 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, Wherein at least one radial Sn solidification structure is present on the surface at 35 mm 2 and the surface roughness Ra of the Sn plating material in the direction perpendicular to the rolling direction is 0.05 탆 or less.

(2) The Cu-Sn alloy layer exposed on the outermost surface has an area ratio of 40% or less, and the exposed Cu-Sn alloy layer has a crystal grain size of 3 m or less when observed from the surface. Sn plating material.

(3) The base material of the copper or copper alloy bath is coated with a Cu undercoat layer or a 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 coating layer 1) or (2).

(4) Sn plating in which an Sn layer is formed on a substrate via a Cu-Sn alloy layer by forming a Sn plating or a Cu and Sn plating layer on the base of a copper or copper alloy tank in this order, Wherein the reflow treatment is performed at a temperature of 300 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, Characterized in that cooling water at 20 to 90 캜 is sprayed and then charged into a water bath at 20 to 90 캜.

(5) An Ni plating layer or a Ni / Cu two-layer lower plating layer is formed on the substrate by forming a Ni, Cu, Sn plating layer in this order on a substrate of copper or a copper alloy bath and then subjected to reflow treatment, -Sn alloy layer, wherein the thickness of the Ni plating layer is 0.05 to 3 mu m, the thickness of the Cu plating layer is 0.05 to 0.5 mu m, the thickness of the Sn plating layer is 0.5 to 1.5 mu m Mu] m, the reflow treatment is performed at a temperature of 300 to 600 DEG C for 1 to 30 seconds, then a cooling water of 20 to 90 DEG C is sprayed, and then the coating is put into a water bath of 20 to 90 DEG C Gt;

(6) An electronic component comprising the Sn plating material according to any one of (1) to (3).

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

Fig. 1 is a schematic cross-sectional view showing a case where the surface roughness of the outermost surface of the Sn plating material is large.
Fig. 2 is a schematic cross-sectional view when the surface roughness of the outermost surface of the Sn plating material is small.
Fig. 3 is a photograph of the outermost surface texture after etching of the Sn plating material when it is put into the water tank after heating by the reflow treatment.
Fig. 4 is a photograph of the outermost surface texture after etching of the Sn plating material when the bath is cooled in a reflow process, followed by bathing in water.
5 is an explanatory diagram of a specular reflectance measurement method.

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 alloy to be a base material of the Sn plating material. As the copper alloy plating, a known copper alloy can be used 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- Alloys, and the like.

(2) radial Sn solidification structure

As described above, by performing the slurry cooling, the molten Sn solidifies in a radial direction. If there is at least one radial Sn solidification structure per 35 mm 2, the surface roughness Ra is 0.05 탆 or less. The number of the radially-oriented Sn solidification structure is not particularly limited in the range in which the effect of the present invention is exhibited, but it is difficult to exceed 10 in the production.

(3) Surface roughness

The surface roughness Ra in the direction perpendicular to the rolling direction on the outermost surface of the Sn plating material after the reflow treatment is set to 0.05 m or less. Preferably, Ra is 0.03 占 퐉 or less, and more preferably Ra is 0.02 占 퐉 or less. If the surface roughness Ra in the direction perpendicular to the rolling direction is excessively large, the generation of the Sn powder can not be suppressed and good surface gloss can not be obtained. The lower limit of the surface roughness is not particularly limited in the range in which the effect of the present invention is exhibited, but it is difficult to make the Ra of less than 0.001 탆.

(4) 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 a Cu-Sn alloy layer is formed below the Sn plating layer. Normally, it has a composition of Cu ₆ Sn ₅ and / or Cu ₃ Sn, but it may contain the above-mentioned components of the base metal and the additive element when the base material is made of a copper alloy.

Since the Cu-Sn alloy layer is hard in comparison with the Sn layer, it is possible to suppress the generation of additional Sn powder by exposing it to the outermost surface of the Sn plating material. However, the area ratio of the Cu-Sn alloy layer exposed on the outermost surface of the Sn plating material is set to 40% or less. , Preferably not more than 35%, more preferably not more than 30%. If the area ratio is too large, the surface roughness Ra of the Sn-plated layer becomes excessively large, and good surface gloss can not be obtained.

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

(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 treatment 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 excessively large, the crystal grain size of the exposed Cu-Sn alloy layer becomes excessively large, and the surface roughness Ra in the direction perpendicular to the rolling direction of the Sn plating layer becomes 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 占 퐉, the effect of Ni plating is not exhibited, and if it exceeds 3 占 퐉, 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. However, 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 process becomes excessively small, and consequently the surface roughness Ra in the direction perpendicular to the rolling direction of the Sn plating layer becomes excessively large, and the area ratio of the Cu- The surface gloss becomes excessively large and good surface gloss can not be obtained. The upper limit of the Sn plating thickness is not particularly limited within the range in which the effects of the present invention are exhibited. However, since the Sn plating thickness is too large, the upper limit is set to 1.5 占 퐉.

The reflow treatment is performed by heating the Sn plating material at a furnace temperature of 300 to 600 ° C for 1 to 30 seconds, spraying cooling water of 20 to 90 ° C onto the surface of the Sn plating material, This is done by injecting ashes.

If the heating temperature is 300 占 폚 and / or the heating time is less than 1 second, the melting of Sn may be insufficient, resulting in unstable production. On the contrary, when the heating temperature is 600 占 폚 and / or the heating time exceeds 30 seconds, the area ratio of the Cu-Sn alloy layer exposed on the outermost surface exceeds 40%, the crystal grain diameter exceeds 3 占 퐉, When the surface roughness Ra in the perpendicular direction is more than 0.05 占 퐉, good surface gloss can not be obtained.

As described above, radial Sn solidification structure is obtained by spraying cooling water after heating. In addition, sprayed water particles adhere to the surface of the heated plating material, and the portion is quenched to inhibit the growth of the Cu-Sn alloy layer. On the other hand, the portion to which the water particles are not adhered is not quenched, so that the growth of the Cu-Sn alloy layer is not suppressed. Therefore, it is possible to cause a difference in the local cooling rate on the surface of the plated layer after heating, and it is also effective to make the crystal grain size of the Cu-Sn alloy layer exposed on the surface of the plated material finer.

Example

Examples are shown below, but the present invention is not intended to be limited to the following examples.

The tough pitch copper was used as a raw material and an ingot to which the respective elements were added so as to be the ratio shown in Table 1 (mass%) was cast and hot-rolled at a temperature of 900 캜 or higher to a thickness of 10 탆, After that, cold rolling and heat treatment were repeated to finish with a plate (substrate) having a thickness of 0.2 mm.

Subsequently, after degreasing and pickling the surface of the substrate, a Ni plating layer and a Cu plating layer are formed in this order by an electroplating method in this order. Ni plating and Cu plating are omitted in some cases, A Sn plating layer was formed. In the case of performing Ni undercoating, electroplating was performed with a sulfuric acid bath (liquid temperature: about 50 캜, current density: 5 A / dm 2), and the thickness of Ni undercoat was set to 0.3 탆. In the case of Cu undercoating, electroplating was performed with a sulfuric acid bath (liquid temperature: about 25 ° C, current density: 30 A / dm 2). The Sn plating was electroplated with a phenol sulfonic acid bath (liquid temperature: about 35 캜, 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 300 to 650 占 폚, cooling water having a temperature of 70 占 폚 was blown out, and then poured into a water bath at 70 占 폚. In some embodiments, the mixture was heated and then put into a water bath at 70 DEG C without bathing.

Each Sn plating material thus obtained was evaluated for various 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) Sn superficial structure on the outermost surface

Sn plating material was immersed in a 65% aqueous solution of phenolsulfonic acid for 5 minutes, and Sn coagulated structure appeared. Thereafter, a range of 35 mm 2 was observed using a microscope (VW-6000 manufactured by Keens Co., Ltd.) Similarly, the number of Sn solidification tissues was measured.

(3) Surface roughness

The surface roughness Ra and the RSm of the Sn plating material in the direction perpendicular to the rolling direction were measured according to JIS B0601 using a cone-shaped microscope (HD100 manufactured by Lasertec Co., Ltd.).

(4) 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 and the area ratio of the Cu-Sn alloy layer is obtained by calculating the area ratio. The binarization was performed by setting 170 out of 255 in the altitude range.

(5) The crystal 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 Nihon FEI Co., Ltd.). Thereafter, 10 randomly selected Cu-Sn alloy layers were selected, and the maximum diameter of each Cu-Sn alloy layer was obtained, and the average diameter of the 10 largest circles was determined as the grain diameter of the Cu-Sn alloy layer Respectively.

(6) Surface gloss

The specular reflectance of the Sn plating material was measured using a digital gloss gloss meter (VG-1D manufactured by Nihon Kogaku Kogyo Co., Ltd.). As shown in Fig. 5, the mirror-reflectance of the Sn-plated material was measured by introducing light at an incident angle of 30 DEG from the transparent portion and reflecting the 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.

(7) Sn powder

The sample was placed on a friction tester (Suga Tester, manufactured by Suga Tester Co., Ltd.), the felt was placed on the surface of the sample, and a load of 30 g weight was applied to the felt. (Scanning distance: 10 mm, scanning speed: 13 mm / s, reciprocation frequency: 30 times).

Thereafter, the surface of the felt on the sample side was observed, and the degree of attachment of the Sn powder was visually evaluated. The evaluation criteria are as follows. If the evaluation is?, There is almost no generation of Sn powder and there is no practical problem, but it is more preferable that it is?.

○: The adhesion of Sn powder to the felt can not be seen.

DELTA: Adhesion of the Sn powder to the felt was observed lightly.

X: The adhesion of the Sn powder to the felt is observed to be deep.

Examples are shown in Tables 2 and 3.

In Examples 1 to 39, all of the Sn plating materials had a surface roughness Ra of 0.05 μm or less on the outermost surface in the rolling direction, a radial Sn solidification structure of 1 or more per 35 mm 2, and a Cu-Sn alloy When the area ratio of the layer was 40% or less and the Cu-Sn alloy layer was exposed to the outermost surface, the grain diameter of the Cu-Sn alloy layer was 3 占 퐉 or less. These Sn plating materials had a mirror-surface reflectance of 70% or more, good surface gloss was obtained, and generation of Sn powder was suppressed.

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 thickness of the Cu undercoating at the time of plating exceeds 0.5 占 퐉. The Cu-Sn alloy layer exposed on the outermost surface had a grain size exceeding 3 占 퐉, Ra in the direction perpendicular to the rolling direction exceeding 0.05 占 퐉, and a specular reflectance of less than 70%.

Comparative Example 3 is an example in which the furnace temperature of the reflow treatment exceeds 600 ° C and the heating time of the reflow treatment exceeds 30 seconds in Comparative Example 4. Both of the both sides have a Sn layer thickness of less than 0.2 占 퐉 after reflow, an area ratio of the Cu-Sn alloy layer exposed on the outermost surface exceeds 40%, a crystal grain size exceeds 3 占 퐉, and an Ra in the direction perpendicular to the rolling direction is 0.05 占 퐉 And the specular reflectance was less than 70%.

Comparative Examples 5 and 6 are examples in which the Cu-Sn alloy layer is not exposed on the outermost surface without bathing. No radial Sn solidification structure was observed, and generation of Sn powder was remarkable.

Comparative Example 7 is an example in which the Cu-Sn alloy layer is slightly exposed on the outermost surface without performing the bathing. The radial Sn solidification structure was not observed, the Ra in the direction perpendicular to the rolling direction exceeded 0.05 mu m, the specular reflectance was less than 70%, and the occurrence of the Sn powder was remarkable.

In Comparative Examples 8 to 11, the Cu-Sn alloy layer was exposed on the outermost surface without bathing. Since the Cu-Sn alloy layer is exposed, generation of Sn powder is suppressed, but radial Sn solidification structure is not observed, Ra in the direction perpendicular to the rolling direction exceeds 0.05 占 퐉, and the specular reflectance is less than 70%. In other words, suppression of the occurrence of Sn powder and good surface luster can not be achieved at the same time.

Claims (6)

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, , Wherein at least one radial Sn solidification structure is present per 35 mm 2, and the surface roughness Ra of the Sn plating material in the direction perpendicular to the rolling direction is 0.05 탆 or less. The method according to claim 1,
Wherein an area ratio of the Cu-Sn alloy layer exposed on the outermost surface is 40% or less and a crystal grain size of the exposed Cu-Sn alloy layer when viewed from the surface is 3 m or less. The method according to claim 1,
A Sn plating material having a base material of a copper or copper alloy tank covered with a Cu undercoating layer or a Ni undercoat layer or a Ni / Cu two-layer undercoat layer in which Ni and Cu are stacked in this order, and having a reflow Sn plating layer thereon. A Sn plating material in which a Sn layer is formed on a substrate via a Cu-Sn alloy layer is manufactured by forming a Sn plating or a Cu and Sn plating layer on a substrate of a copper or copper alloy tank in this order and then performing a reflow treatment Wherein the reflow treatment is carried out at a temperature of 300 to 600 ° C for 1 to 30 seconds and then a reflow treatment is carried out at a temperature of 20 to 90 ° C for 1 to 30 seconds while the Cu plating layer has a thickness of 0 to 0.5 μm and the Sn plating layer has a thickness of 0.5 to 1.5 μm, Lt; RTI ID = 0.0 > C, < / RTI > and then putting it in a water bath at 20 to 90 deg. A Ni plating layer or a Ni / Cu two-layered lower plating layer is formed on the substrate by forming a Ni, Cu, Sn plating layer on the substrate of copper or a copper alloy in this order and then subjected to reflow treatment to form a Cu- 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, and the thickness of the Sn plating layer is 0.5 to 1.5 占 퐉 , Heating the reflow treatment at a temperature of 300 to 600 占 폚 for 1 to 30 seconds, spraying cooling water of 20 to 90 占 폚, and then introducing the refractory treatment into a water bath of 20 to 90 占 폚. An electronic part comprising the Sn plating material according to any one of claims 1 to 3.

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