JP2005126763A - Coating material, electric/electronic component using the same, rubber contact component using the same, and coating material manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating material which is low in friction coefficient and contact resistance, excellent in oxidation resistance, and has consistent characteristic for a long time. <P>SOLUTION: In the coating material having a conductive base material 3, and a coating layer 4 formed on the base material 3, the coating layer 4 contains Sn and an intermetallic compound with noble metals at least on a surface 4a side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a covering material, a manufacturing method thereof, and an electric / electronic component and a rubber contact part using the covering material. More specifically, the present invention relates to a coating material that has good friction characteristics and heat resistance and is suitable as a material for connector parts or contact parts used in a high temperature environment such as an engine room of an automobile. In addition, the present invention relates to a covering material that suppresses an increase in contact resistance over time and is suitable as a material for rubber contact parts including conductive rubber.

Coating materials comprising a substrate and a coating layer covering the substrate surface are used in various technical fields. And according to the technical field, the material of a base material, a coating layer, etc. are selected suitably.
For example, in electronic / electric parts such as connector parts and contact parts incorporated in electric / electronic circuits, etc., a coating material in which a base material made of Cu or Cu alloy is coated with metal Sn is used.

  Among these coating materials, those used for electric and electronic parts for automobiles have good heat resistance, that is, low contact resistance at room temperature, that is, at high temperatures. However, it is required that the contact resistance can be kept low. Further, it is desired that the covering material used for the connector part is a material that reduces a load when the connector part is connected, that is, an insertion force. And in the keyboard of a personal computer etc., about the coating | covering material which comprises a contact component with conductive rubber, it is desired to have long-term stability.

Conventionally, as a coating material having good heat resistance, a coating material having an intermediate layer made of an intermetallic compound represented by the general formula Ni ₃ Sn is known between a coating layer made of metal Sn and a Cu base material. (For example, refer to Patent Document 1).
Moreover, as a connector component that can be fitted with a low insertion force, there is known one in which the thickness of the coating layer made of metal Sn is optimized and the thickness is reduced (see, for example, Patent Document 2).

Furthermore, as a coating material having long-term stability, a material in which the crystal grain size of metal Sn contained in the coating layer is optimized is known (for example, see Patent Document 3).
JP-A-4-329891 (Claims etc.) Japanese Patent Laid-Open No. 10-302864 (claims) JP-A-5-308152 (Claims etc.)

However, the coating material described in Patent Document 1 has a relatively high contact resistance due to the reaction of the metal Sn contained in the coating layer with other elements diffused from the substrate side at a high temperature exceeding 150 ° C., for example. It is converted into a high alloy such as CuSn alloy or a compound and the low contact resistance state disappears.
Although the coating material described in Patent Document 2 is effective for reducing the insertion force, the thickness of the coating layer is thin at a high temperature, so that the metal Sn is more easily than in the case of the coating material of Patent Document 1. Will be converted to other alloys and lose its function.

Therefore, there is a problem that it is difficult to say that the heat resistance of the coating materials described in Patent Documents 1 and 2 is at a satisfactory level.
Moreover, the coating material described in Patent Document 3 generates a natural oxide film having a high contact resistance on the surface of the coating layer even in a room temperature environment of about 25 ° C., for example, and its thickness increases with time.
Thus, even if the coating material described in Patent Document 3 is used in a room temperature environment, the metal Sn is converted into an oxide from the surface side over time. When viewed, there is a problem that it is difficult to say that it always has long-term stability.

  The present invention solves the above-mentioned problems, has a low contact resistance, has a low friction coefficient, is effective in reducing the insertion force, and has excellent oxidation resistance and stable characteristics over a long period of time. An object is to provide a material and a manufacturing method thereof. Furthermore, this invention aims at provision of the coating | covering material which has favorable heat resistance, and its manufacturing method. Still further, the present invention aims to provide electrical / electronic parts using these coating materials, and more specifically, to provide connector parts, contact parts, and rubber contact parts.

In order to achieve the above-described object, in the present invention, in a covering material provided with a conductive base material and a coating layer formed on the base material, the coating layer is at least on the surface side, Sn and A covering material characterized by containing an intermetallic compound with a noble metal is provided.
As a specific aspect, the noble metal is Ag and the intermetallic compound is Ag ₃ Sn (Claim 2).

It is preferable that the coating layer further includes an intermetallic compound of Ni and Sn on the base material side.
According to the present invention, there is provided an electrical / electronic component characterized in that the electrical / electronic component interposed in the electrical circuit includes the coating material according to claim 3 (claim 4).
As a specific aspect, the electric / electronic component is a connector component or a contact component (Claim 5), and is inserted in an electric circuit installed in an automobile (Claim 6).

In the present invention, the insulating substrate, at least two coating materials according to any one of claims 1 to 3 disposed on the insulating substrate, and the surface of the coating layer of the at least two coating materials. A rubber contact part is provided, which is disposed so as to be capable of being pressed together at the same time, and includes a conductive rubber for electrically connecting the covering materials when pressed against the covering layer.
Moreover, in this invention, it is provided with the base material which has electroconductivity, and the coating layer formed in the said base material, The said coating layer manufactures the coating | covering material which contains the intermetallic compound of Sn and Ag at least on the surface side In the method, a film forming step for forming a film containing Sn and Ag on the substrate, and a heat treatment for converting the film containing Sn and Ag formed in the film forming step into the coating layer by performing a heat treatment And a process for producing a covering material characterized in that it comprises a step.

Prior to the film formation step, a film containing Ni is preferably formed on the substrate.
As a specific aspect, in the film forming step, an Sn film containing Sn and an Ag film containing Ag are sequentially formed on the base material (claim 10). Diffusion processing (claim 11).

The coating material of the present invention has a low coefficient of friction and contact resistance, excellent oxidation resistance, and exhibits stable characteristics over a long period of time. Therefore, this covering material is suitable as a material for rubber contact parts.
Furthermore, the coating material of the present invention further has good heat resistance, and is suitable as a material for connector parts and contact parts that are arranged in a high temperature or sulfur-rich environment such as in an automobile engine room.

FIG. 1 shows a covering 2 according to the first embodiment of the present invention. This covering material 2 can be used, for example, as a material for various electric / electronic components.
The covering material 2 includes a base material 3 having conductivity. The material of the base material 3 is not particularly limited. For example, when the coating material 2 is used as an electrical / electronic component such as a connector component or a contact component, the material of the base material is appropriately selected according to the mechanical strength, heat resistance, and conductivity required for the component. Can do. More specifically, examples of the material of the base material include copper alloys such as pure copper, phosphor bronze, brass, western white, beryllium copper and Corson alloy, iron alloys such as pure iron and stainless steel, and various nickel alloys. be able to. Furthermore, the base material may be a composite material in which the surface of a material made of these materials is coated with copper, cobalt, nickel, or the like. Further, the base material may be a polymer material or ceramic material having conductivity, or may be a composite material obtained by coating a polymer material or ceramic material having insulation properties with a conductive material. Of these materials, pure copper or a copper alloy is suitable as the base material.

  Moreover, the shape and manufacturing method of the base material 3 are not particularly limited, and the base material is, for example, a wire material, strip material, ribbon material, and the like manufactured by rolling, forging, slitting, or pressing. It may be a plate material or the like. Further, the base material may be a pattern made of a conductor formed on the insulating substrate by appropriately combining plating, masking, and etching.

A coating layer 4 is formed on at least one surface of the substrate 3. The covering layer 4 may be formed on both surfaces of the base material 3.
In the coating material 2 of the present invention, Sn element and Ag are formed on the surface 4a side of the coating layer 4 opposite to the base material 3, that is, on the surface 4a side of the coating layer 4 exposed in the coating material 2. An intermetallic compound containing elements (hereinafter referred to as SnAg intermetallic compound) is included.

This SnAg intermetallic compound is represented by the general formula Ag ₃ Sn, and is a stable compound having a low contact resistance and good oxidation resistance. Therefore, the coating material of the present invention is suitable as a material for contact parts that require stable characteristics over a long period of time.
Here, including the SnAg intermetallic compound on the surface 4a side of the coating layer 4 means including at least the surface 4a and the vicinity thereof. The reason is that the properties of this region have the greatest influence on the contact resistance and oxidation resistance of the coating material. Note that the SnAg intermetallic compound may be included throughout the thickness of the coating layer 4.

  The existence form of the SnAg intermetallic compound contained in the coating layer 4 is not particularly limited. For example, as shown in FIG. 2, the uppermost layer portion of the coating layer 4 may be a single layer 4 </ b> A made of a SnAg intermetallic compound. Or you may exist disperse | distributing in Sn-Ag alloy, for example. Alternatively, the SnAg intermetallic compound may be contained in a diffusion layer generated by subjecting the formed coating layer to a film containing Sn element and a film containing Ag element, which will be described later. . In the case of being dispersed and present in the diffusion layer, the concentration of the SnAg intermetallic compound has a gradient in the depth direction toward the substrate 3 side of the coating layer 4. You may do it.

The abundance ratio of Ag in the coating layer 4 is 1% by mass or more, more preferably 3.5% by mass or more with respect to the total of Sn and Ag. Moreover, it is preferable that it is 73 mass% or less. Because, if it is less than 1% by mass, a remarkable effect cannot be expected. Further, if it is 3.5% by mass or more, it exceeds the eutectic composition of the Sn-Ag alloy, so that the SnAg intermetallic compound precipitates in a granular form, especially when manufactured by reflow treatment, and contributes to stabilizing the low contact resistance. To do. On the other hand, if the Ag content exceeds 73% by mass, Ag becomes larger than the composition of Ag ₃ Sn, which causes migration and sulfurization.

FIG. 3 shows an example of the rubber contact part 8 according to the second embodiment of the present invention, and the rubber contact part 8 is used by being incorporated in, for example, a keyboard, a mobile phone, a remote controller or the like.
The rubber contact part 8 includes an insulating substrate 10. An electric circuit is formed on the surface of the insulating substrate 10. This electric circuit is a pattern made of a conductor such as copper, which is formed by sequentially performing plating, masking, and etching on the insulating substrate 10, and the pattern includes at least two covering materials that are separated from each other. 2 is included. That is, the coating layer 4 is formed on the surface of the conductor 3 as a base material.

  A hollow hemispherical rubber material 12 is disposed on the insulating substrate 10 so as to cover these two coating materials 2, and the rubber material 12 can be elastically deformed. A conductive rubber 14 is bonded and fixed inside the top of the rubber material 12. The conductive rubber 14 is made of, for example, a base material made of various rubbers and a conductive material such as carbon powder or metal powder contained in a dispersed state in the base material. On the other hand, an intermediate member 16 is disposed above the rubber member 12, and a key member 18 is disposed above the intermediate member 16.

According to this rubber contact component 8, when the key member 18 is pushed down, the rubber material 12 is crushed through the intermediate material 16, so that the conductive rubber 14 is formed on the surfaces of the coating layers 4 of the two coating materials 2. Weld together. Then, the two covering materials 2 are electrically connected through the pressed conductive rubber 14.
By the way, recently, soft touch is desired for a keyboard or the like, and the contact pressure between the conductive rubber 14 and the covering material 2 tends to decrease. Therefore, the coating layer 4 is required to have a natural oxide film that is difficult to generate and grow on the surface for a long period of time. This is because the conductive rubber 14 is soft and hardly pierces the natural oxide film having a high contact resistance existing on the surface of the coating layer 4 when being slidably contacted or abutted against the surface of the coating layer 4. Because it is possible.

  Further, in mobile phones, remote controllers, and the like, the current has been reduced to save power, and the coating layer of the coating material is required to have a lower contact resistance. Therefore, like the coating material of the present invention, the coating material having excellent oxidation resistance, so that a thick natural oxide film is hardly generated on the surface, and the coating material having a coating layer with low contact resistance is a rubber contact. It is suitable as a material for parts.

Note that the surface side of the coating layer 4 exposed in the coating material 2 contains an intermetallic compound of Sn element and noble metal instead of the intermetallic compound containing Sn element and Ag element. Also good. This is because the intermetallic compound of the Sn element and the noble metal has low contact resistance and long-term stability like the SnAg intermetallic compound.
Here, examples of the noble metal include, in addition to the Ag element, a white metal element composed of Ru, Rh, Pd, Os, Ir, and Pt, and an Au element.

Moreover, when using the coating | covering material 2 as a raw material of rubber contact components, it is preferable that the thickness of the coating layer 4 is 1-3 micrometers. When the thickness is thinner than 1 μm, the oxidation resistance may be deteriorated. When the thickness is more than 3 μm, the oxidation resistance is not only saturated but also the material cost and the manufacturing cost are increased. .
FIG. 4: has shown the disassembled perspective view of Example 20 of the multipolar connector component for motor vehicles based on 3rd embodiment of this invention.

  The multipolar connector part 20 includes a male housing 22 and a female housing 24 which are made of resin and are fitted to each other. Between the male housing 22 and the female housing 24, a pair of key members 26 and 28 for fixing between these housings are inserted. Further, 16 male terminals 30 or 16 female terminals 32 are fitted on the opposite sides of the male housing 22 and the female housing 24 from the key members 26 and 28, respectively. In the drawing, one male terminal 30 and one female terminal 32 are shown in order to avoid complicated lines.

  The male terminal 30 and the female terminal 32 are formed by pressing the covering material described in the first embodiment of the present invention into a predetermined shape and then bending it so that they can be fitted to each other at one end side. At the time of this fitting, the covering layer located on the tongue piece portion of the male terminal 30 and the covering layer located on the tube portion of the female terminal 32 are in sliding contact with each other for a predetermined length. Further, the core wire of the covered electric wire 34 is caulked and fixed to the other end side of each of the male terminal 30 and the female terminal 32.

Hereinafter, the operation of the covering material of the present invention in the above-described automotive connector part will be described.
Sn has a high diffusion rate and is easily alloyed with other elements contained on the substrate side, and the alloying proceeds from the interface between the substrate and the coating layer toward the surface of the coating layer. Therefore, in the case of a conventional coating layer made of metal Sn, the thickness is designed and formed in advance so that the metal Sn still remains on the surface side of the coating layer even after such alloying occurs. It had been.

  On the other hand, according to the coating layer of the coating material of the present invention, the Sn element is contained as an intermetallic compound with the Ag element, and this mainly defines the characteristics of the coating layer. Therefore, according to this coating layer, it is not necessary to increase the thickness of the coating layer as a countermeasure against the Sn element being alloyed with other elements as in the prior art, and the thickness can be reduced. This is not only to reduce the cost by saving the material, that is, Sn, but also in the case of a connector part including such a thin coating layer, since the deformation resistance of the coating layer at the time of connection is reduced, the insertion force It is effective for reducing the above. In particular, in the case of a multi-pole connector part for automobiles in which a plurality of terminals are integrated with the improvement of automobile performance in recent years, the reduction of the insertion force at each terminal leads to the reduction of the insertion force as a whole connector part. This is effective for reducing the burden on workers who connect the multipolar connector parts.

The SnAg intermetallic compound is not only a low-cost material, but also exhibits good sulfidation resistance when compared to metal Ag. Therefore, the coating material of the present invention has an atmosphere containing a relatively large amount of sulfur. It is suitable as a material for connector parts and contact parts for automobiles used therein.
Furthermore, the SnAg intermetallic compound is a stable compound in which migration of Ag element is suppressed when compared with metal Ag, and has a property that whiskers made of metal Ag that causes insulation failure are difficult to grow. Therefore, the coating material of the present invention is suitable because it can prevent a short circuit between adjacent male terminals or between female terminals generated through whiskers when used as a material for the above-described multipolar connector part for automobiles. is there.

In the coating material of the present invention, the coating layer preferably contains a NiSn intermetallic compound composed of Sn element and Ni element on the substrate side.
The NiSn intermetallic compound is represented by the general formula Ni ₃ Sn _n (where n = 1, 2, 4), and already contains Sn element. Therefore, the SnSg intermetallic compound is Sn from the SnAg intermetallic compound existing on the surface side of the coating layer. The effect which prevents an element from diffusing to the base material side is exhibited. Therefore, the Sn element in the SnAg intermetallic compound contained in the coating layer is difficult to reduce. The action of preventing the diffusion of Sn element of the NiSn intermetallic compound is effectively exhibited even in a high temperature environment exceeding 150 ° C., and the SnAg intermetallic compound is converted into another compound even at such a high temperature. To suppress that. Therefore, the coating material of the present invention further including a NiSn intermetallic compound on the substrate side of the coating layer is suitable as a material for electric / electronic parts for automobiles used in a high temperature environment.

  Note that the existence form of the NiSn intermetallic compound contained in the coating layer is not particularly limited. For example, as shown in FIG. 5, the lowermost layer portion of the coating layer 4 may be a single layer 4B made of a NiSn intermetallic compound. Alternatively, for example, they may be dispersed in a Ni—Sn alloy. Alternatively, the NiSn intermetallic compound may be contained in a diffusion layer generated by subjecting the formed coating layer to a film containing Sn element and a film containing Ni element, which will be described later. . In the case of being dispersed and present in the diffusion layer as described above, the concentration of the NiSn intermetallic compound has a gradient in the depth direction toward the substrate 3 side of the coating layer 4. You may do it.

The average thickness of this NiSn intermetallic compound is preferably 0.1 μm or more and 0.5 μm or less. This is because if the thickness is less than 0.1 μm, the above-described effects are not sufficiently exhibited, and if the thickness exceeds 0.5 μm, there is a demerit such that cracking easily occurs during bending.
Hereinafter, the manufacturing method of the coating | covering material of this invention is demonstrated.
In the coating material of the present invention, after a film containing Sn element and Ag element (hereinafter also referred to as SnAg film) is formed on the surface of a substrate that has been appropriately cleaned, It can be manufactured by heat treatment.

  This film forming step may consist of two steps, a step of forming an Sn film on the surface of the substrate and a step of forming an Ag film on the Sn film. You may consist of one process which forms into a base material surface the SnAg alloy film which consists of a SnAg alloy containing Ag element. However, in the case where the film forming process includes two processes, the Sn film may be formed on the Ag film after the Ag film is first formed on the surface of the substrate.

Here, the Sn film, the Ag film, and the SnAg alloy film may contain elements other than Sn and Ag, respectively, but the content of other elements in that case is SnAg metal by heat treatment. It should be limited to the extent that does not prevent the formation of intermetallic compounds.
Note that the film formation method employed in the preliminary film formation step and the film formation step is not particularly limited, but the wet plating method is preferable because it is low-cost and suitable for mass production.

  In the heat treatment step performed after the film formation step, the film formed on the substrate is heated, whereby the Sn element diffuses and reacts with the Ag element to form an SnAg intermetallic compound. Examples of such heat treatment include re-melting treatment that is heated at a temperature equal to or higher than the melting point of metal Sn, that is, reflow treatment, and thermal diffusion treatment that is heated at a temperature lower than the melting point of metal Sn. For example, the material to be treated is heated in a combustion gas in the case of reflow treatment and then water-cooled. In the case of thermal diffusion treatment, the material to be treated is in a non-oxidizing atmosphere such as an inert gas such as nitrogen gas or a combustion gas. And heated at a temperature of 100 ° C. or higher for several hours.

  Further, when manufacturing a coating material provided with a coating layer further containing a NiSn intermetallic compound on the substrate side, a preliminary film for forming a Ni film containing Ni element on the substrate surface prior to the above-described film forming step. A film formation process may be performed. In the film forming process, an SnAg film containing Sn element and Ag element is formed on the Ni film formed in the preliminary film forming process. Again, the method for forming the Ni film is not particularly limited, but the wet plating method is preferable because it is low cost and suitable for mass production.

  In that case, the conditions of the above-described heat treatment step are appropriately set so that not only the SnAg intermetallic compound but also the NiSn intermetallic compound is formed. For example, if a heating condition of a temperature of 100 ° C. or higher and 1 hour or longer is employed, a stable NiSn intermetallic compound is generated on the substrate side of the coating layer, that is, near the interface between the Ni film and the SnAg film. If a heating condition of a temperature of 150 ° C. or more and 3 hours or more is employed, a stable single layer made of a NiSn intermetallic compound can be formed in the vicinity of the interface between the Ni film and the SnAg film. Therefore, it is more preferable to employ the latter heating condition in order to generate both intermetallic compounds by a single heat treatment.

  The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the use of the coating material of the present invention is not limited to the above-described embodiment.

Examples A2-A5, A7, A8, Comparative Examples A1, A6
On the cleaned copper ribbon, a Ni film made of metallic Ni was formed by electroplating in a preliminary film forming step. Thereafter, in the film forming step, an Ag film made of metal Ag and an Sn film made of metal Sn were formed on the Ni film in this order by electroplating. However, for A8 only, the Sn film was formed first and the Ag film was formed later. Then, the copper ribbon that has undergone the preliminary film forming process and the film forming process is subjected to a reflow process in a combustion gas at 700 ° C. in a heat treatment process, and then subjected to a water cooling process, and Examples A2 to A5, A7, A8 The coating materials of Comparative Examples A1 and A6 were prepared. The plating conditions at this time are shown in Table 1, and the thicknesses of the Ni film, the Ag film, and the Sn film formed in the preliminary film forming process and the film forming process are shown in Table 2. Table 2 also shows the value obtained by converting the thickness of the Ag film into the surface concentration and the ratio of Ag to the total of Sn and Ag.

The following evaluation was performed about the manufactured coating material of each Example and a comparative example.
(1) Evaluation of contact resistance (i) After heating test Each coating material was subjected to a heating test in which heat treatment was performed at a temperature of 160 ° C for 120 hours, and then the contact resistance of the surface on the coating layer side was measured. The contact resistance was measured by a four-terminal method, and was measured using a 6φ Ag probe under the conditions of DC 10 mA and a load of 0.98 N. The measurement results are shown in Table 3 and FIG. The measurement was performed 10 times for each of the examples and comparative examples.

(Ii) After Sulfurization Test Each coating material was exposed to an environment containing 3 ppm hydrogen sulfide at a temperature and relative humidity of 40 ° C. and 95% for 24 hours, and then the contact resistance was measured. The measurement results are shown in Table 3 and FIG. The measurement method and its conditions are the same as in the case (i) above. The measurement was performed 10 times for each of the examples and comparative examples.

(2) Evaluation of dynamic friction coefficient The dynamic friction coefficient of the coating layer of the coating material was measured as an index of the insertion force when connecting the connector parts. The measurement results are shown in Table 3, and the results of Examples A4 and A7 and Comparative Examples A1 and A6 are shown in FIG. The measurement was performed using a Bowden friction tester under the conditions of a load of 294 mN, a sliding distance of 10 mm, a sliding speed of 100 m / min, and a sliding number of one time. In addition, as a counterpart material of the coating material, that is, a probe, a brass strip having a thickness of 0.25 mm having a reflow-treated Sn plating having a thickness of 1 μm on the surface and 0.5 mmR of overhanging processing was used.

(3) Evaluation of Presence Form of SnAg Intermetallic Compound and NiSn Intermetallic Compound in Coating Layer FIG. 9 shows cross-sectional TEM photographs immediately after the reflow of the coating material of Example A4 and after the heating test. It can be seen that the SnAg intermetallic compound is formed in a granular form on the surface of the coating layer, and the SnNi intermetallic compound is formed in a layer form.
In addition, in FIG. 9, the boundary of each phase was shown with the white dotted line.

The following is clear from Table 3 and FIG.
(1) The contact resistance of the coating layer of the coating material after the heating test decreases rapidly as the film thickness of the Ag film, that is, the surface concentration of Ag in the coating layer after the heat treatment increases. This is considered to be because the Sn element and the Ag element formed a SnAg intermetallic compound and the Ni element and the Sn element formed a NiSn intermetallic compound by the heat treatment.
(2) More specifically, when the surface concentration of Ag element in the coating layer is 0.004 g / m ² or more, the contact resistance is 10 mΩ or less even after the heating test. Therefore, in order to improve the heat resistance of the coating material, the surface concentration of Ag in the coating layer is preferably 0.004 g / m ² or more. In order to make the surface concentration of Ag 0.004 g / m ² or more, when an Ag film made of metal Ag is formed in the film forming process, the average thickness of the Ag film is about 0.0004 μm or more. You can do it.

The following is clear from Table 3 and FIG.
(1) The contact resistance of the coating material after the sulfidation test was independent of the film thickness of the Ag film before the heat treatment step, that is, the surface concentration of the Ag element in the coating layer within the evaluated range. This is considered to be because in the range of the surface concentration of the Ag element evaluated, the amount of metal Ag contained in the coating layer was small even on the upper side of the range, and the amount of silver sulfide generated by the sulfidation test was small. It is done.
(2) Based on such considerations, it is considered that when the surface concentration of the Ag element is high beyond this range, the ratio of the metal Ag increases, and the sulfidation or migration of the metal Ag is likely to occur. Thus, in addition to these considerations, considering that the Ag element and the Sn element form an intermetallic compound represented by the general formula Ag ₃ Sn, the number of Ag atoms contained in the coating layer is included in the coating layer. The number of Sn atoms is preferably 3 times or less.

From Table 3 and FIG. 8, the following is clear.
The coating materials of Examples A1 to A5 and Examples A7 to A8 have a low dynamic friction coefficient of 0.4 or less. Therefore, if these coating materials are used, a connector component that can be connected with a small insertion force can be manufactured. Since the dynamic friction coefficient tends to increase as the thickness of the Sn film increases, it can be understood that the thickness of the Sn film is better if only the dynamic friction coefficient is taken into consideration.

Examples B1 to B8, Comparative Examples B9 and B10
An electrolytic degreasing treatment and a pickling treatment were first applied as pretreatment to a 7/3 brass strip having a thickness of 0.3 mm. A film having the composition and thickness shown in Table 4 (hereinafter referred to as a base film) was formed on the pretreated brass strip by an electroplating method in a preliminary film forming step. Thereafter, in the film forming process, two films having the compositions and thicknesses shown in Table 4 were sequentially formed on the base film by electroplating. Of these two films, the base film side is referred to as a first film, and the film formed on the first film is referred to as a second film.

And with respect to the brass strip which passed through these preliminary | backup film-forming processes and a film-forming process, it heat-processes on the conditions shown in Table 4 by the heat treatment process in nitrogen atmosphere, Example B1-B8 and Comparative Example B9, A coating material for B10 was prepared.
The plating conditions at this time are shown in Table 5.

(1) Evaluation of contact resistance and (2) Evaluation of dynamic friction coefficient were performed on the manufactured coating materials of each of the examples and comparative examples. Furthermore, the following (4) insulation resistance evaluation was performed on these coating materials. These results are shown in Table 6.
(4) Evaluation of insulation resistance As an evaluation of insulation resistance, the ease of growth of whiskers that cause a short circuit was examined. That is, after the coating materials of each Example and Comparative Example were left in an air bath at a temperature of 50 ° C. for 1 month, the presence or absence of whiskers was examined by microscopic observation.

From Table 6, the following is clear.
(1) After the heating test and after the sulfidation test, the contact resistances of the coating materials of Examples B1 to B7 each including the NiSn intermetallic compound and the SnAg intermetallic compound in the coating layer are low values of 10 mΩ or less. However, it becomes higher compared to Examples A2 to A5, A7 and A8 which are reflowed as a whole. The reason for this is that, since the reflowed SnAg intermetallic compound in the coating layer is granular as shown in the photograph in FIG. It can be realized.
(2) On the other hand, the coating material of Example B8 which does not contain the NiSn intermetallic compound in the coating layer and contains the SnAg intermetallic compound has a contact resistance exceeding 10 mΩ after the heating test. This is because the coating layer does not contain a NiSn intermetallic compound, and the SnAg intermetallic compound contained in the coating material of Example B8 is other compound such as SnCu intermetallic compound as compared with Examples B1 to B7. It is thought that it was easy to convert to. From this, in order to improve the heat resistance of the coating material, it can be seen that the coating layer preferably contains a NiSn intermetallic compound.

(3) In the case of the coating material of Example B1 in which the heat diffusion is insufficient and, therefore, the formation of SnAg intermetallic compound is insufficient, the contact resistance after the heating test and after the sulfidation test is 10 mΩ or less. It is not possible to completely suppress the occurrence of
(4) In the coating material of Example B5 in which Ag is coated on the outermost surface and diffused, the contact resistance after the heating test is good, but the contact resistance after the sulfidation test is relatively high. . This is thought to be due to the presence of Ag remaining without becoming an intermetallic compound on the surface. Therefore, depending on the film thickness of Ag, it is more preferable to coat the Ag film under the Sn film. It can be seen that the reflow treatment for melting the Sn film is more preferable as the crystallization means.

(5) The coating materials of Examples B1 to B8 exhibit a low dynamic friction coefficient of 0.4 or less except for Example B4. Therefore, by using these coating materials, it is possible to manufacture a connector component that is excellent in heat resistance and sulfidation resistance and that can be connected with a small insertion force. Here, the dynamic friction coefficient tends to increase as the thickness of the Sn film formed in the film forming process increases. Therefore, considering only the dynamic friction coefficient, the thinner the Sn film formed in the film forming process, the better. More specifically, the thickness of the Sn film is 1.0 μm or less. Is preferred.
(6) In the coating materials of Examples B2 to B7, no occurrence of whiskers was observed. In addition, in the coating materials of Example B1 and Comparative Example B9, a small amount of whiskers was observed. On the other hand, although the coating layer contains a Sn—Ag alloy, many whiskers were observed in the coating material of Comparative Example B10 that did not contain a SnAg intermetallic compound. From this, it can be seen that in order to improve the insulation resistance of the coating material, it is necessary that the coating layer contains a SnAg intermetallic compound and has undergone a sufficient heating step.

Examples D1 to D18, Comparative Examples D19 to D24
A base film having the composition and thickness shown in Tables 7 and 8 was formed by electroplating on the washed brass ribbon in the preliminary film forming step. Thereafter, in the film forming process, two films having the compositions and thicknesses shown in Table 7 and Table 8 were sequentially formed on the base film by electroplating. Of these two films, the base film side is referred to as a first film, and the film formed on the first film is referred to as a second film.

For Example D15 and Example D16, the base film is composed of two films, of which the base-side film is referred to as the first base film, and the other film formed on the first base film. The film is referred to as a second base film.
Table 9 shows the plating conditions at this time.
Then, the brass strips that have undergone the preliminary film forming process and the film forming process are subjected to a reflow process in a combustion gas at 700 ° C. in a heat treatment process, and then subjected to a water cooling process, and Examples D1 to D18 and Comparative Example D19 are performed. A coating material of -D24 was prepared.

However, the coating materials of Comparative Examples D22 and D23 were not subjected to heat treatment such as reflow treatment.
In addition, the coating material of Example D17 was not subjected to reflow treatment in the heat treatment step, but was subjected to heat diffusion treatment in which heat treatment was performed in a nitrogen atmosphere at a temperature of 150 ° C. for 3 hours.
And about the coating | covering material of Example 18, the immersion process to the solution was given as a melt | dissolution process process after the heat processing process. By this dissolution treatment step, the surface of the coating layer was dissolved and removed by about 0.1 μm. This solution is, for example, a liquid obtained by mixing sulfuric acid having a concentration of 80 g / L and a hydrogen peroxide aqueous solution having a concentration of 10 mL / L. In addition, as a dissolution treatment step for dissolving the surface of the coating layer in this way, an electrolytic dissolution treatment may be employed instead of the immersion treatment. This electrolytic dissolution treatment is performed using, for example, a 6-fold diluted aqueous solution of hydrochloric acid or a mixed solution of sulfuric acid having a concentration of 90 g / L and potassium fluoride having a concentration of 5 g / L.

  About the manufactured coating material of each Example and the comparative example, (1) evaluation of contact resistance mentioned above, (2) evaluation of a dynamic friction coefficient, and (4) evaluation of insulation resistance were performed. These results are shown in Tables 10-15.

From Table 10, the following is clear.
(1) The film containing Sn element and Ag element is subjected to reflow treatment, and the coating materials of Examples D1 and D2 containing SnAg intermetallic compound have low contact resistance after the heating test or after the sulfidation test.
(2) On the other hand, the coating materials of Comparative Examples D19 to D23 in which the coating layer does not contain the SnAg intermetallic compound have a large contact resistance after the heating test or after the sulfurization test. This is due to Sn or the oxidation of Cu or Ni element diffused on the surface or the sulfurization of Ag element.
Therefore, it can be seen that the coating layer containing the SnAg intermetallic compound has a stable contact resistance over a long period of time compared to the coating layer containing only one of the Ag element and the Sn element.

From Table 11, the following is clear.
(1) When the coating materials of Example D2, Example D4, and Example D8 are compared, the magnitude of the contact resistance of the coating material is almost the same as the order of film formation of the Sn film and the Ag film in the film formation process. Dependence.
(2) Further, when comparing the coating materials of Examples D3 to D7, the magnitude of the contact resistance of the coating material is almost independent of the surface concentration of Ag in this range.

From Table 12, it can be seen that the contact resistance of the coating material after the sulfidation test is independent of the composition of the base film. In addition, the contact resistance of the coating material after the heating test proves advantageous when the base film is made of an iron group element such as Ni, Co, or Fe.
From Table 13, it can be seen that, even if an Au film containing Au element or a Pd film containing Pd element is formed instead of an Ag film containing Ag element, a coating material showing stable contact resistance over a long period of time can be obtained. Understand. This is probably because noble metals such as Au and Pd also form an intermetallic compound with Sn.

From Table 14, if SnAg intermetallic compound is contained on the surface side of the coating layer, the contact resistance after the heating test or the sulfidation test becomes low even if the base film is composed of two films. I understand that. In addition, the friction coefficient is expected to be small.
It can also be seen that the Ag film and the Sn film may each be a film made of an alloy containing another element as long as it contains an Ag element or Sn element.

From Table 15, it can be seen that in the heat treatment step for generating the SnAg intermetallic compound in the film containing Ag element and Sn element, thermal diffusion treatment may be adopted in addition to the reflow treatment. However, reflow treatment is advantageous to prevent whisker generation.
In addition, when the surface of the coating layer is slightly dissolved and removed by the dissolution treatment step as in Example D18, the metal Sn can be selectively removed to increase the ratio of SnAg intermetallic compound on the surface, so that the contact resistance varies. Can be suppressed. Therefore, it is preferable to use the coating material for the dissolution treatment step.

It is sectional drawing of the coating | covering material of 1st embodiment of this invention. It is explanatory drawing of the one presence form of the SnAg intermetallic compound contained in the coating | covering material of FIG. It is sectional drawing of the rubber contact component of 2nd embodiment of this invention. It is a partial disassembled perspective view of the multipolar connector part for motor vehicles of 3rd embodiment of this invention. It is explanatory drawing of the suitable example of the coating | covering material used for the multipolar connector component for motor vehicles of FIG. It is a graph which shows the relationship between the surface concentration of Ag element after a heating test of the coating material of one Embodiment of this invention, and contact resistance. It is a graph which shows the relationship between the surface concentration of Ag element and the contact resistance after the sulfidation test of the coating material of one Embodiment of this invention. It is a graph which shows the relationship between the thickness of Sn film in the coating layer of the coating material of one Embodiment of this invention, and a dynamic friction coefficient. The left of Sn-Ag alloy film in the coating layer of the coating material of one Embodiment of this invention: Immediately after reflow, Right: It is a cross-sectional photograph after heat processing.

Explanation of symbols

3 Base material 4 Coating layer 4a Surface of coating layer

Claims (11)

In a covering material comprising a base material having conductivity and a coating layer formed on the base material,
The covering layer contains an intermetallic compound of Sn and a noble metal at least on the surface side. The coating material according to claim 1, wherein the noble metal is Ag, and the intermetallic compound is Ag ₃ Sn. The said coating layer is a coating | covering material of Claim 2 which further contains the intermetallic compound of Ni and Sn in the said base material side.   An electric / electronic component interposed in an electric circuit, comprising the covering material according to claim 3.   The electrical / electronic component according to claim 4, wherein the electrical / electronic component is a connector component or a contact component.   6. The electric / electronic component according to claim 4, wherein the electric circuit is installed in an automobile.   An insulating substrate, at least two coating materials according to any one of claims 1 to 3 disposed on the insulating substrate and spaced apart from each other, and a surface of the coating layer of the at least two coating materials are arranged so as to be capable of being pressed simultaneously. A rubber contact component comprising conductive rubber for electrically connecting the covering materials when pressed against the covering layer. In the method for producing a coating material comprising a conductive substrate and a coating layer formed on the substrate, the coating layer containing an intermetallic compound of Sn and Ag on at least the surface side,
A film forming step of forming a film containing Sn and Ag on the substrate;
A method of manufacturing a coating material, comprising: a heat treatment step in which a film containing Sn and Ag formed in the film formation step is subjected to a heat treatment to be converted into the coating layer.   The manufacturing method of the coating | covering material of Claim 8 which forms the film | membrane containing Ni on the said base material prior to the said film-forming process.   The method for manufacturing a coating material according to claim 8 or 9, wherein in the film forming step, an Sn film containing Sn and an Ag film containing Ag are sequentially formed on the base material.   The method for manufacturing a coating material according to claim 8, wherein the heat treatment is a reflow treatment or a thermal diffusion treatment.