JP4814552B2 - Surface treatment method - Google Patents

Description

  The present invention, for example, a surface of a multi-pin connector used for an electric wiring of an automobile or the like, a surface that requires both heat resistance and reduced wear and friction coefficient during insertion and removal, and charging of an electric vehicle Require high wear resistance / corrosion resistance, such as sockets that allow a large current flow, such as sockets, surfaces that require contact with rotating bodies such as motor brushes, and wear resistance. The present invention relates to the surface treatment of electrical and electronic parts that require solderability such as the surface to be connected and the connection of a printed circuit board, and the manufacturing method thereof.

With the recent development of electronics, electrical wiring has become more complex and highly integrated, and accordingly, the number of connectors has been increased. In addition, the thermal environment is becoming increasingly severe, such as heat generated from the outside and Joule heat.
A conventional Sn-plated connector has a problem in that the frictional force increases when the connector is inserted and removed, making it difficult to insert the connector. Furthermore, the Sn plating material is inferior in heat resistance because Cu diffuses from the material and the underlying plating due to thermal effects, and the contact resistance increases due to the formation of the Cu-Sn compound layer and its oxide film. Even in storage by, deterioration of solderability due to diffusion and oxidation was a problem.
Conventionally, as a measure to reduce the insertion force of the Sn-plated terminals with multiple pins, hard Ni plating or the like is applied to the base of Sn plating, or a Cu-Sn diffusion layer is provided to improve the base hardness and diffusion barrier effect Proposals aimed at have been proposed.

However, when Sn plating is performed on Ni plating, the contact resistance of the Ni—Sn alloy or its oxide generated after the heating test is large and the heat resistance is poor. Further, when Sn is dug up and Ni is exposed when the terminal is inserted, the Ni oxide significantly deteriorates the contact resistance after heating. In addition, since Ni base plating is usually applied in an amount of about 1 to 2 μm, there is a drawback that cracks and the like are likely to occur during bending at the time of terminal molding. Even if the Ni base plating is thinned to about 0.5 μm, the increase in the contact resistance cannot be solved.
When a Cu—Sn diffusion layer is used for the intermediate layer, the contact resistance increases due to long-term heating, or the soldering property is inferior. Also in the manufacturing method, there is a method using thermal diffusion as a method of leaving Sn on the surface layer and providing a Cu—Sn diffusion layer on the inner side, but it is difficult to control the thickness of the diffusion layer. , The progress of diffusion due to the temperature environment during use is inevitable, and heat resistance is poor. The proposal of Sn plating after forming the Cu—Sn diffusion layer requires an extremely complicated process, and is not practical because it is inferior in cost and surface Sn plating adhesion and formability.

In addition, current electric vehicles require charging once or more a day, and it is necessary to ensure wear resistance of the charging socket parts. On top of that, a large current of 10 A or more flows, so that the heat generation is large, and the conventional method such as Sn plating causes problems such as peeling of the plating.
Furthermore, for connection of printed circuit boards, there is a demand for solderability that is even better than conventional Sn plating materials for the transition to Pb-free high-temperature solder and the transition to flux with low activity as environmental measures. . Specifically, it is necessary that the solderability is not deteriorated even by humidity or high temperature during storage.
It has become clear that conventional surface treatment methods cannot cope with the above problems. Further, in the surface treatment proposed by the present invention, the coating of Sn or Sn alloy layer, Cu-Sn alloy layer or further Cu layer, and Ni or Ni alloy layer and its coating method have been conventionally proposed. The optimal combination and the optimal thickness were not considered.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that an Sn or Sn alloy layer is formed on the outermost surface, and a Cu—Sn alloy layer (Cu ₃ Sn, Cu ₄ Sn, Cu ₆ Sn ₅ or the like Cu is formed on the inner surface thereof. An alloy layer containing Sn intermetallic compound, an alloy layer such as Cu-Sn-Ni in which Ni of the base is thermally diffused, etc., and in some cases, a Cu layer left by the reaction may be provided, and Ni inside Or by forming the Ni alloy layer appropriately to the desired thickness, it is suitable for, for example, multi-pin connectors and electric vehicle charging sockets, has low heat resistance, low friction coefficient, excellent wear resistance, and solderability The inventors have found that a surface-treated film having an excellent surface can be obtained, and have completed the present invention.

  That is, according to the present invention, firstly, an Sn- or Sn-alloy layer having a thickness X of 0.05 to 2 μm on the outermost surface, and an intermetallic mainly composed of Cu—Sn having a thickness Y of 0.05 to 2 μm inside An alloy layer containing a compound and a Ni or Ni alloy layer having a thickness Z of 0.01 to 1 μm are formed on the inner side of the alloy layer. After heating at 160 ° C. for 1000 hours, rolling with R = 0.2 mm by JIS H 3110 A film characterized by having heat-resistant adhesion that does not cause peeling by peeling with a tape after performing a 90 ° W bending test in the direction and the vertical method; second, 0.2X ≦ Y ≦ 5X, and 0 .05Y.ltoreq.Z.ltoreq.3Y. Third, a Cu layer having a thickness of 0.7 .mu.m or less between the alloy layer containing the intermetallic compound and the Ni or Ni alloy layer. A coating according to 1 or 2; The film according to any one of 1 to 3, wherein at least the surface layer of the material to be coated with the film is Cu or Cu alloy; fifth, the Ni or Ni alloy layer in order from the surface side on the material surface; A method for producing a coating film according to any one of claims 1 to 4, wherein a heat treatment is performed after the Cu layer, Sn or Sn alloy layer is coated; sixth, Ni on the material surface in order from the surface side; Or a method for producing a coating film according to any one of 1 to 4, wherein the Ni alloy layer, Cu layer, Sn or Sn alloy layer is coated, and then reflow treatment is performed; A Ni or Ni alloy layer, a Cu layer, a Sn or Sn alloy layer were coated in order from the surface side on the surface of the material having a point average roughness of 1.5 μm or less and a center line average roughness of 0.15 μm or less. It is characterized by heat treatment afterwards The method for producing a coating according to any one of 1 to 4; eighth, on the surface of the material having a ten-point average roughness of 1.5 μm or less and a centerline average roughness of 0.15 μm or less in surface roughness The method for producing a coating according to any one of 1 to 4, wherein a reflow treatment is performed after coating the Ni or Ni alloy layer, Cu layer, Sn or Sn alloy layer in order from the surface side; The manufacturing method according to any one of 5 to 8, wherein the surface of the raw material is coated with Cu or a Cu alloy layer in advance before the Ni or Ni alloy layer is coated; 4. An electric / electronic component coated with the coating according to any one of 4; 11th, an Sn or Sn alloy layer having a thickness X of 0.05 to 2 μm on the outermost surface, and a thickness on the inner side thereof Intermetallic compound mainly composed of Cu-Sn with Y of 0.05-2 μm An alloy layer containing an object, and further a Ni or Ni alloy layer having a thickness Z of 0.01 to 1 μm is formed on the inner side thereof, and coats the surface of a Cu alloy material containing Ni and Sn Twelfth, the surface of the Cu alloy material containing Ni and Sn is coated with the Ni or Ni alloy layer, the Cu layer, the Sn or Sn alloy layer in this order from the surface side, and then reflow treatment is performed. A method for producing a coating according to the eleventh aspect; thirteenthly, provides an electrical and electronic component characterized in that the surface of a Cu alloy material containing Ni and Sn is coated with the coating according to the eleventh.

  As will be apparent from the examples described later, the surface treatment according to the present invention and the manufacturing method thereof, and the electric and electronic parts obtained by these methods are excellent in friction resistance, molding processability, solderability, and after long-term heating. Connector material that can handle high density of recent automobile electrical components, etc., and printed circuit board connection connectors that require wear resistance, solderability, etc. It is excellent as a material for electrical and electronic parts.

The contents of the present invention will be specifically described. The reason for limiting the numerical range of the present invention will be described.
First, regarding the thickness of the outermost Sn layer, if the thickness is less than 0.05 μm, the stability of the contact resistance and the solderability deteriorate. In particular, the contact resistance at low load tends to become unstable, and the solderability deteriorates due to moisture and temperature during storage. Further, there is a problem of corrosion resistance degradation such as corrosion due to H ₂ S or SO ₂ or corrosion due to NH ₃ gas in the presence of moisture. When the thickness of the Sn layer exceeds 2 μm, problems such as an increase in insertion force resistance due to digging friction during terminal insertion, a decrease in fatigue characteristics, and an economical disadvantage arise. Furthermore, the thickness of the Cu—Sn diffusion layer obtained by heat treatment to be formed on the inside becomes too thick, and a decrease in molding processability such as cracking during processing is recognized. Therefore, the thickness of the Sn layer is in the range of 0.05 to 2 μm. Furthermore, a preferable range is 0.1 to 1 μm.

  Here, the Sn layer may be formed by any method such as plating, melt dipping, shot peening, and cladding, but plating is desirable from the viewpoint of thickness control and cost. Moreover, the thickness of Sn layer here is the thickness of Sn layer of the outermost surface after the diffusion process by heat processing etc. is completed, and is the part of the outer side (surface side) of a Cu-Sn intermetallic compound layer. . However, 20 wt% or less of elements other than Sn may be included due to the influence of the diffusion treatment. If elements other than Sn are contained in excess of 20 wt%, problems may occur in solderability and contact resistance after long-term heating. Furthermore, Sn coated on the outermost surface before the diffusion treatment may be alloy plating such as Sn—Cu, Sn—Ag, Sn—Bi, Sn—Zn, Sn—Pb, or melt dipping such as Sn—In. However, Cu, Ag, Bi, Zn, Pb, In, etc. in Sn diffuses to the outermost surface when diffusion treatment is performed in which an alloy layer containing a Cu—Sn intermetallic compound is provided on the inside or by long-term heating. Even so, it is important not to lower the solderability and the contact resistance.

  In addition, an alloy layer containing a Cu—Sn intermetallic compound having a thickness of 0.05 to 2 μm is required as a base for Sn coating. The alloy layer containing the Cu—Sn intermetallic compound is preferably formed by heat treatment using an underlying Cu coating, for example, Cu diffusion from Cu plating, and alloying with Sn coated on the surface. Therefore, Cu remaining after the reaction is included. However, the plating thickness remaining as Cu is preferably 0.7 μm or less, and more preferably 0.3 μm or less. Excess Cu diffuses by long-term heating, grows a Cu-Sn diffusion layer, decreases the Sn thickness of the outermost layer, and decreases contact resistance and solderability.

The alloy layer containing the Cu—Sn intermetallic compound thus obtained further effectively suppresses the diffusion of Ni from the inner side (underlying side), and the Ni—Sn alloy layer and its oxide are formed on the surface. Is effectively suppressed. Thereby, the increase in contact resistance after long-term heating can be suppressed. Furthermore, the alloy layer containing a hard Cu—Sn intermetallic compound also contributes to the effect of reducing the insertion force. In order to efficiently exhibit such an effect, a thickness of 0.05 μm or more, preferably 0.1 μm or more is required.
However, if the alloy layer containing the Cu—Sn intermetallic compound is too thick, the workability is significantly reduced. In addition, since the Cu—Sn diffusion layer produced by diffusion increases the surface roughness, even if the Sn coating of the outermost layer portion is adjusted, it is easy to adversely affect the appearance roughness and insertion force. Therefore, the preferable Cu—Sn thickness is 2 μm or less, more preferably 1 μm or less.

Furthermore, it is necessary to coat Ni or a Ni alloy layer on the inner side (underlayer) of the alloy layer containing a Cu—Sn intermetallic compound. This Ni or Ni alloy layer not only effectively suppresses the diffusion of Cu when copper or a copper alloy is used as the material, but also effectively suppresses the diffusion of additive elements in the copper alloy, It effectively prevents the solderability and the heat resistance adhesion of the film from decreasing. For example, Zn in brass and P in phosphor bronze.
In addition, this Ni or Ni alloy layer has an effect of improving insertion force resistance, heat resistance, corrosion resistance and the like in combination with an alloy layer containing a Cu—Sn intermetallic compound thereon. This Ni or Ni alloy layer is often formed by plating, but any method may be used as in the case of Sn described above. Further, Ni may be coated or Ni alloy may be coated. Ni-Co, Ni-P, etc. are mentioned as Ni alloy performed by electroplating. Further, during the heat treatment for obtaining the Cu—Sn diffusion layer, an alloy layer such as Ni—Cu may be formed by diffusing with the material or Cu plating.

In addition, the material can be applied to materials other than copper and copper alloys such as steel materials, stainless steel, and aluminum alloys. In this case, in order to improve the adhesion of Ni or Ni alloy film, Cu base plating can be performed, but since diffusion of Cu from the base plating can be effectively suppressed, contact resistance change during long-term heating and Degradation of solderability can be effectively suppressed.
In general, the electric and electronic parts are preferably made of copper or a copper alloy in consideration of necessary properties such as electric conductivity, springiness, and magnetism, but are not limited thereto as described above. When the material is copper or copper alloy, from the base side, Ni or Ni alloy, (Cu), Cu-Sn intermetallic compound, Sn or Sn alloy, or Cu or Cu alloy, Ni or Ni alloy , (Cu), an alloy containing a Cu—Sn intermetallic compound, a Sn or Sn alloy layer structure.

When the material is a copper alloy, Zn: 0.01 to 50 wt%, Sn: 0.1 to 12 wt%, as a preferable range of additive elements from the viewpoint of strength, elasticity, electrical conductivity, workability, corrosion resistance, etc. Fe: 0.01-5 wt%, Ni: 0.01-30 wt%, Co: 0.01-5 wt%, Ti: 0.01-5 wt%, Mg: 0.01-3 wt%, Zr: 0.01 -3 wt%, Ca: 0.01-1 wt%, Si: 0.01-5 wt%, Mn: 0.01-20 wt%, Cd: 0.01-5 wt%, Al: 0.01-10 wt%, Pb : 0.01-5 wt%, Bi: 0.01-5 wt%, Be: 0.01-3 wt%, Te: 0.01-1 wt%, Y: 0.01-5 wt%, La: 0.01- 5 wt%, Cr: 0.01-5 wt%, Ce: 0.01-5 wt%, Au: 0 01~5wt%, Ag: 0.01~5wt%, P: comprises at least one element of 0.005 to 0.5%, it is desirable that the total amount thereof is 0.01~50wt%.
In consideration of recyclability as a raw material, it is desirable that the copper alloy contains Ni and Sn.

Next, the thickness of each layer and the reason for the limitation will be described.
The thickness (X) of the outermost Sn or Sn alloy layer, the thickness (Y) of the alloy layer containing an intermetallic compound mainly composed of Cu-Sn inside thereof, and the thickness of the Ni or Ni alloy layer inside thereof (Z), and the optimum value of each thickness is as described above. However, it has been found that it is desirable to limit the thickness ratio because there is an interaction between the respective surface treatments.
Specifically, it is optimal for diffusion of each element due to long-term heating, response to electrical performance deterioration due to oxidation, resistance to digging resistance when inserting a terminal, response to increased insertion force due to adhesion, response to wear and corrosion, etc. The film thickness ratio is obtained. The film thickness ratio is desirably as follows.
0.2X ≦ Y ≦ 5X (1) Formula
0.05Y ≤ Z ≤ 3Y (2) If the film thickness ratio exceeds the upper limit or less than the lower limit, contact resistance after heating, solderability after moisture resistance test, terminal insertion force resistance, wear amount, corrosion resistance Etc. will drop, and all will not be satisfied. Therefore, it is important to make the film thickness satisfying the expressions (1) and (2).

Next, in terms of the surface roughness of the material, it is preferable that the ten-point average roughness is 1.5 μm or less and the center line average roughness is 0.15 μm or less by a measuring method based on JIS B 0601. By limiting the surface roughness of the material, the surface smoothness of each layer coated on the material is stabilized, and the adhesion and appearance are improved. Moreover, when plating, it is effective also in heat resistant adhesiveness and film thickness distribution.
In particular, the surface roughness of the material is defined by a surface coated with Cu or a Cu alloy as occasion demands, and further coated with Ni or a Ni alloy, Cu, Sn or Sn alloy, followed by a heat treatment such as reflow. Contributes to the stability of the subsequent appearance and surface roughness. The surface roughness after reflow is preferably such that the ten-point average roughness is 1.0 μm or less and the center line average roughness is 0.1 μm or less.

Further, the thickness of the oxide film of the material itself is important in forming each layer. In particular, in the case of forming a film by plating in relation to the pretreatment, it affects the adhesion, appearance, void generation at the time of diffusion, etc., so the oxide film of the material should be 20 nm or less, preferably 12 nm or less. is there.
Accordingly, the Sn or Sn alloy layer having a thickness of 0.05 to 2 μm on the outermost surface and a metal mainly composed of Cu—Sn having a thickness of 0.05 to 2 μm inside and satisfying the formula (1) To effectively obtain a heat-resistant film composed of an alloy layer containing a compound or further Cu, and further Ni or a Ni alloy layer satisfying the formula (2) having a thickness of 0.01 to 1 μm inside thereof Can do.

Next, a manufacturing method will be described.
A method for effectively obtaining the configuration of the present invention will be described in detail below.
First, a material whose surface roughness and oxide film thickness are adjusted is prepared, and in some cases, Cu is coated. When the material is copper or a copper alloy, the underlying Cu coating can be omitted. Hereinafter, plating, which is a desirable method of coating, will be described as an example.
Ni or Ni alloy is plated on the material or Cu-plated material. However, it is necessary to sufficiently perform cleaning such as degreasing and pickling in consideration of adhesion. Next, Cu plating is performed. However, in order to improve the appearance and adhesion after Cu plating, it is desirable to perform pickling between the steps of Ni plating and Cu plating.
Then, Sn or Sn alloy plating is performed on the outermost layer. Thus, it is important to take the basic structure of Ni, Cu, and Sn from the base side.

Next, Cu of the intermediate plating and Sn on the outermost surface are diffused to obtain a Cu—Sn diffusion layer. This treatment is preferably combined with a reflow treatment for melting the outermost Sn. Specifically, Sn and Cu—Sn diffusion layers having a desired thickness can be obtained by making the heat pattern during the reflow process appropriate. However, the intermediate Cu plating only needs to have a thickness for forming the Cu—Sn diffusion layer, and is not required as an excessive thickness left by the reaction. Specifically, the thickness remaining as Cu is preferably 0.7 μm or less, and more preferably 0.3 μm or less. Excess Cu diffuses by long-term heating, grows a Cu-Sn diffusion layer, decreases the Sn thickness of the outermost layer, and decreases contact resistance and solderability.
The reflow treatment conditions are preferably a temperature of 300 to 900 ° C. and a condition of 1 to 300 seconds. At temperatures lower than 300 ° C. or temperatures exceeding 900 ° C., it is difficult to control both reflow and diffusion at the same time. In particular, the temperature factor is important in terms of a good surface state and oxidation suppression, and a control of the thickness of the diffusion layer and a suppression of abnormal diffusion in which the diffusion layer grows abruptly. The atmospheric gas can be appropriately selected depending on the reflow method. The main reflow methods include a burner method, a hot air circulation method, an infrared method, and a Joule heat method, but any method may be used. However, although the heating time varies depending on these methods, if less than 1 second, a sufficient diffusion layer cannot be obtained, and if the time exceeds 300 seconds, the effect is saturated and the cost becomes disadvantageous.

  Further, the thickness of the oxide film after Sn reflow is desirably as thin as possible, but the thickness is desirably 30 nm or less. If the thickness of the oxide film on the surface exceeds 30 nm, the contact resistance increases and becomes extremely unstable and the electrical performance deteriorates. Furthermore, the solderability and the adhesion of the oxide film may be reduced, and peeling may occur in subsequent processing. A more preferable oxide film thickness is 20 nm or less. Here, the oxide film is mainly composed of tin oxide. This oxide film is formed by diffusion of an element added to Sn, Cu in a Cu—Sn diffusion layer, Ni or an Ni alloy element as a base, or copper as a material. What diffused the additive element contained in a base alloy includes what formed complex oxide with Sn.

The oxide formed on such a surface has an effect of improving wear resistance and slipperiness in combination with the underlying Cu—Sn diffusion layer, Ni or Ni alloy layer. However, since the surface oxide adversely affects contact resistance and solderability, it is preferable to control the surface oxide thinly.
The film constituted as described above can be applied to either or both of the male side and the female side when applied to the male and female terminals of the electrical component. Furthermore, it may be applied only to necessary portions.

  Examples of the present invention will be described below.

[Example 1] In Table 1, the surface treatment material No. 1-16 were prepared. However, all the means for forming each layer were performed by electroplating. Specifically, Ni was a nickel sulfamate bath, Cu was a copper sulfate bath, and Sn was a sulfate bath. Moreover, pickling was performed in the steps before and after the Ni plating.
However, no. 9, 10 and 15 are Ni, No. 11 is Ni, Cu, No. 11; 12 is Cu. No. 16 did not perform Sn plating (the bar is drawn to the film thickness in Table 1).
The material used is a rolled material of 0.25 mm thick copper alloy containing 1 wt% Ni, 0.9 wt% Sn, and 0.05 wt% P. The surface roughness is 0.9 μm with a 10-point average roughness of 0.9 μm. The center line average roughness was 0.08 μm, and the thickness of the oxide film of the material was about 7 nm, which was a value sufficiently smaller than 20 nm.

Next, the reflow conditions were changed, and a continuous reflow process was performed at 450 to 700 ° C. for 4 to 20 seconds, and a diffusion layer was formed simultaneously with the reflow process. From the measurement results of AES and ESCA, the thickness of the outermost oxide film after the reflow is No. Nos. 1 to 14 are about 3 to 8 nm. 15 and 16 were both about 15 nm, and both samples were sufficiently smaller than 30 nm. Further, the surface roughness was 10-point average roughness of 0.2 to 0.7 μm and center line average roughness of 0.05 to 0.10 μm.
The thickness of each layer was dissolved one by one from the surface layer side by an electrolytic method, and measured by an X-ray film thickness meter and an electrolytic method. Furthermore, for thin materials, an analyzer such as an Auger electron spectrometer (AES) or a photoelectron spectrometer (ESCA) was used in combination, or the cross section was observed with a transmission electron microscope (TEM) and measured. Further, the thickness of each layer was measured while confirming the consistency with the target electrodeposition amount obtained by calculation. And about the film | membrane (Sn <0.05micrometer, Cu-Sn <0.05micrometer, Cu <0.05micrometer) which could not be confirmed as a film thickness, it displayed as ND.

The friction coefficient measurement, molding processability, soldering test, heat-resistant adhesion, contact resistance, and discoloration of the test materials obtained as described above were investigated.
As shown in FIG. 1, the friction coefficient is measured using the same surface at a speed of 100 mm / min while applying a load of 15 N to the surface treatment plate material provided with three indents with an inner radius R = 1 mm. It moved on the processed lower board | plate material, the frictional force was measured with the load cell, and the friction coefficient was calculated.
Forming workability was evaluated by performing a 90 ° W bending test (JIS H 3110, R = 0.2 mm, rolling direction and vertical direction), and observing the mountain surface of the central part of the sample with a 24 × stereo microscope. In addition, cracks when indented to measure the friction coefficient were also observed with a 24 × stereo microscope. The case where no crack was observed in both tests was evaluated as “◯”, and the case where crack was observed in either processing was evaluated as “×”.

Solderability was tested in accordance with MIL-STD-202F-208E using an inactive flux after 1 hour exposure to boiling steam. The test results were evaluated as ○ when less than 95% was wet, and x when less than 95%.
Heat resistant adhesion was evaluated by heating at 160 ° C. for 1000 hours and then performing a 90 ° W bending test (JIS H 3110, R = 0.2 mm, rolling direction and vertical direction), and then tape peeling. did. The case where peeling did not occur due to peeling was marked with ○, and the case where peeling occurred was marked with ×. At the same time, the degree of discoloration of the surface was visually observed, and those markedly discolored with respect to those before heating were evaluated as x.
The contact resistance test was measured by a four-terminal method using a low current low voltage measuring device after heating the sample at 160 ° C. for 1000 hours. The maximum load of the Au contact was 0.5 N, and the resistance value at this time was measured.
The above evaluation results are shown in Table 2.

From the results of Tables 1 and 2, No. 1 according to the present invention is obtained. The materials 1 to 8 have a small coefficient of friction and are excellent, and are excellent in molding processability, solderability, film adhesion after a heating test, contact resistance, and discoloration resistance. Therefore, it can be said that the present invention has extremely excellent characteristics for applications such as recent multi-pin connectors, charging sockets, printed circuit board connection parts, and the like.
On the other hand, no. Nos. 9 and 10 have a large friction coefficient and are inferior in terms of contact resistance and discoloration after heating. No. No. 11 does not perform the underlying Ni plating and intermediate plating Cu, but forms a diffusion layer with the raw material Cu and the surface Sn, but with a small friction coefficient, solderability, contact resistance after heating Inferior in terms of discoloration.

No intermediate plating of Cu and no Cu—Sn diffusion layer. No. 12 is inferior in terms of solderability, contact resistance after heating, and discoloration.
No. with thick Ni No. 13 is inferior in moldability and has a thick Sn. No. 14 is inferior in friction coefficient, has no Ni layer, and has a thick Cu—Sn diffusion layer. No. 15 is inferior in terms of moldability, solderability, contact resistance after heating, and discoloration. No. with no Sn. No. 16 is inferior in terms of solderability, contact resistance after heating, and discoloration.

[Example 2] Each layer was formed by electroplating in the same manner as in Example 1. However, no. Nos. 17, 18, and 21 are made of a kind of brass (plate thickness 0.8 mm). Nos. 19, 20, and 22 were made of phosphor bronze (plate thickness: 0.2 mm). In addition, the surface roughness of each of the ten-point average roughness is 1.0 and 0.9 μm, and the center line average roughness is 0.13 and 0.08 μm. The value was 8 nm, which was sufficiently thinner than 20 nm.
Next, reflow treatment was continuously performed at an ambient temperature of 350 to 800 ° C. for a time of 5 to 20 seconds, and Cu—Sn diffusion was formed simultaneously with the reflow treatment to prepare the sample. The friction coefficient measurement, molding processability, soldering test, heat-resistant adhesion, contact resistance, and discoloration of the obtained test material were investigated in the same manner as in Example 1.

As is apparent from Tables 3 and 4, No. 1 of the present invention is obtained. Nos. 17 to 20 have a small coefficient of friction and are excellent, and are excellent in moldability, solderability, film adhesion after a heating test, contact resistance, and discoloration resistance. Therefore, it can be said that the effect of the present invention does not change even if the material is brass or phosphor bronze.
On the other hand, no. Nos. 21 and 22 have a large coefficient of friction and are inferior in terms of contact resistance and discoloration after heating. In particular, no. No. 22 is inferior in the adhesion of the film after heating. Comparison with 19 and 20 shows that the effect of the present invention is extremely large.

Example 3 Each layer was formed on the material used in Example 1 by electroplating in the same manner as in Example 1. No. In Nos. 23, 24 and 27, the outermost plating is Sn alloy plating. Nos. 23 and 27 have Ni as the base and No. 23. For 24, the base was Ni alloy plating. No. Nos. 25, 26 and 28 have Sn as the outermost plating. For 25, 26 and 28, the base was Ni alloy plating.
As Sn alloy plating, Sn-10 wt% Zn was plated using an organic complex salt bath. As Ni alloy plating, phosphorous acid was added to the Watt bath, and Ni-5 wt% P was plated.

As in Example 1, reflow conditions were appropriately selected and reflowed. As a result, Zn in the Sn—Zn alloy plating diffused on the surface and formed an oxide centered on zinc oxide, which had a particularly large effect on contact resistance. Did not give. The oxide film thickness was about 5 to 11 nm, which was a value smaller than 30 nm.
In addition, No. Nos. 23 to 26 produced Cu—Sn diffusion layers due to the heat effect of reflow. Since 27 and 28 did not have a Cu layer, a Ni—Sn diffusion layer was formed instead of a Cu—Sn diffusion layer.

As apparent from Tables 5 and 6, No. 1 of the present invention. Nos. 23 to 26 have a small coefficient of friction and are excellent, and are excellent in moldability, solderability, film adhesion after a heating test, contact resistance, and discoloration resistance. Therefore, it can be said that the effect of the present invention does not change even if the Sn layer on the surface is made of Sn alloy or the Ni layer is made of Ni alloy.
On the other hand, No. without a Cu—Sn intermediate layer. No. 27 is inferior in solderability and contact resistance after heating. No. 28 is inferior in terms of moldability, solderability, film adhesion after heating, contact resistance and discoloration. Therefore, it can be seen that the effect of the present invention is extremely large.

It is a figure which shows the measuring method of a friction coefficient.

Explanation of symbols

1 Upper test piece with indent 2 Lower test piece 3 Weight (15N)
4 Horizontal table 5 Pulley 6 Load cell

Claims (3)

On the surface of the material having a 10-point average roughness of 1.5 μm or less and a center line average roughness of 0.15 μm or less in surface roughness , Ni or Ni having a thickness of 0.17 to 0.63 μm in order from the surface side A surface treatment method characterized by subjecting an alloy layer, Cu layer, Sn or Sn alloy layer to a reflow treatment at a temperature of 450 to 700 ° C. for 4 to 20 seconds . The surface treatment method according to claim 1, wherein a Cu or Cu alloy layer is coated on the material surface in advance before coating the Ni or Ni alloy layer . The surface treatment method according to claim 1 , wherein the material is a Cu alloy material containing Ni and Sn.

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