JP6967993B2 - Electrical contact materials and switches using them - Google Patents

Description

The present invention relates to an electrical contact material and a switch using the same.

Copper or copper alloys plated with precious metals, which have excellent contact resistance, are used as electrical contact materials for smartphones and automobiles. Of these, silver-plated copper or copper alloys are often selected in terms of cost and reliability.

While silver plating has a small contact resistance, it has a problem that it easily corrodes in a sulfurized atmosphere and the contact resistance increases. To solve such a problem, an electric contact material in which silver plating is subjected to surface treatment such as rust prevention treatment or inorganic coating has been developed for the purpose of suppressing deterioration of silver plating characteristics.

For example, Patent Document 1 describes an electrical contact material in which a coating layer of silver or a silver alloy is provided on a metal base material, and palladium or the like or an alloy thereof is coated on the coating layer with a thickness of 0.01 to 2.0 μm. be written.

Further, in Patent Document 2, a first layer made of silver or a silver alloy, a second layer mainly composed of nickel, cobalt or an alloy thereof and having a thickness of 0.001 to 0.20 μm is described on a conductive substrate. , And an electrical contact material mainly composed of palladium or a palladium alloy and having surface layers having a thickness of 0.001 to 0.4 μm laminated in this order.

Further, as an alternative to silver plating, there is an example of providing palladium plating having solder wettability equivalent to that of silver plating. For example, in Patent Document 3, a first base layer such as nickel is formed on the surface of a copper or copper alloy substrate, a second base layer such as nickel is formed on the first base layer, and a surface of a noble metal such as palladium is formed on the first base layer. Described are conductive materials for electronic components in which the layers are formed to a thickness of 0.002 to 0.5 μm.

Japanese Unexamined Patent Publication No. 63-22517 Japanese Patent No. 3956841 Japanese Unexamined Patent Publication No. 9-330827

However, in the configuration of Patent Document 1, although the palladium plating thickness of the surface layer is specified, the state of the palladium film on the surface layer is not specified.

Further, in the electric contact material of Patent Document 2, although the effect of suppressing the increase in contact resistance in a sulfurized atmosphere was observed, the adhesion between the mold resin such as an epoxy resin or a silicone resin and the electric contact material is good. It could be reduced. This is because the heat generated when the resin is cured causes nickel in the second layer immediately below the surface layer to thermally diffuse and move to the surface layer, thereby weakening the adhesion between the resin and the electrical contact material. Is likely to be due to.

Further, in the conductive material for electronic parts of Patent Document 3, although the adhesion between the conductive material for electronic parts and the mold resin is maintained, the contact resistance is inferior to that of the conventional silver-plated electrical contact material. There was something.

An object of the present invention is that the contact resistance is equivalent to that of a silver-plated electrical contact material, the adhesion to the mold resin is good, and the corrosive gas invades through the gap between the mold resin and the mold resin even in a sulfide atmosphere. It is an object of the present invention to provide an electric contact material capable of preventing an increase in contact resistance of a contact portion in a switch for a long period of time and a switch using the same.

The gist structure of the present invention is as follows.
[1] A conductive substrate containing copper, a first layer containing nickel or cobalt formed on at least one surface of the conductive substrate, a second layer containing silver formed on the first layer, and the above. An electrical contact material having a third layer containing palladium formed on the second layer, and having a palladium atomic number concentration of the surface layer quantified by Auger electron spectroscopy of 50.0% or more.
[2] The electrical contact material according to the above [1], wherein palladium is present in a speckled dispersed state in the SEM-EDX measurement of the surface layer.
[3] The electrical contact material according to the above [1] or [2], wherein the average thickness of the third layer is in the range of 0.001 μm or more and 0.100 μm or less.
[4] The electrical contact material according to any one of the above [1] to [3], wherein the average thickness of the second layer is within the range of 0.01 μm or more and 1.00 μm or less.
[5] The electrical contact material according to any one of the above [1] to [4], wherein the average thickness of the first layer is in the range of 0.01 μm or more and 1.00 μm or less.
[6] The electronic contact material according to any one of [1] to [5], wherein the surface layer has a share strength with the resin of 8.0 MPa or more.
[7] A switch using the electrical contact material according to any one of the above [1] to [6].

According to the present invention, it has a contact resistance equivalent to that of a silver-plated electric contact material, has good adhesion to a mold resin, and corrosive gas invades through a gap with the mold resin even in a sulfurized atmosphere. It is possible to suppress an increase in the contact resistance of the contact portion in the switch for a long period of time.

It is sectional drawing which shows typically the electric contact material which concerns on this invention. 6 is an SEM-EDX mapping image of Pd in the electrical contact material of Example 1.

Hereinafter, the present invention will be described in detail based on the embodiments.

The electrical contact material according to the present invention includes a conductive substrate containing copper (Cu), a first layer containing nickel (Ni) or cobalt (Co) formed on at least one surface of the conductive substrate, and the first layer. A surface layer having a second layer containing silver (Ag) formed on the layer and a third layer containing palladium (Pd) formed on the second layer and quantified by Auger electron spectroscopy. The palladium atom number concentration is 50.0% or more.

FIG. 1 is a cross-sectional view schematically showing an electrical contact material according to the present invention. As shown in FIG. 1, in the electrical contact material 10, the first layer 2 is provided on the surface of the conductive substrate 1, the second layer 3 is provided on the surface of the first layer 2, and the surface of the second layer 3 is provided. The third layer 4 is provided. In this way, the first layer 2, the second layer 3, and the third layer 4 are coated on the conductive substrate 1 in this order.

As the conductive substrate, copper or a copper alloy having excellent conductivity and heat dissipation is preferable.

For example, as an example of a copper alloy, "C26800 (Cu-35% Zn)", "C51910 (Cu-6% Sn-P)" and "C52120 (Cu-8% Sn-), which are alloys published in CDA (Copper Development Association)". "P)", "C71500 (Cu-30% Ni)", "C52100 (Cu-8% Sn-0.03% P)" and the like can be used. The number before each element and% indicate mass%. Since these copper alloys have different conductivity and strength, they are appropriately selected according to the characteristics required for the electrical contact material. From the viewpoint of improving conductivity and heat dissipation, it is preferable to use a copper alloy having a conductivity of 5% IACS or more.

The thickness of the conductive substrate is not particularly limited, but is usually within the range of 0.03 mm or more and 1.00 mm or less, preferably 0.03 mm or more and 0.10 mm or less.

Examples of the metal or alloy forming the first layer include nickel, nickel alloy, cobalt, cobalt alloy, nickel cobalt alloy and the like.

Here, the role of the first layer is to suppress the diffusion of copper, which is a component of the conductive substrate, into the second layer, and to improve the adhesion between the conductive substrate and the second layer. In particular, when the second layer is formed by a plating treatment using a metal that is nobler than the conductive substrate, the first layer, which is a base layer, is provided in advance by a base treatment such as flash plating or strike plating before the plating treatment. It is effective to improve the adhesion and prevent the substitution precipitation.

The average thickness of the first layer is preferably in the range of 0.01 μm or more and 1.00 μm or less, more preferably 0.05 μm or more and 0.50 μm or less. When the average thickness of the first layer is 0.01 μm or more, the above effect is sufficiently improved. Further, when the average thickness of the first layer is 1.00 μm or less, the amount of the raw material required for forming the first layer is suppressed.

Examples of the metal or alloy forming the second layer include silver and silver alloys. The role of the second layer is to reduce the contact resistance of the electrical contact material.

The average thickness of the second layer is preferably in the range of 0.01 μm or more and 1.00 μm or less, more preferably 0.20 μm or more and 0.80 μm or less. When the average thickness of the second layer is 0.01 μm or more, the contact resistance is sufficiently low. Further, when the average thickness of the second layer is 1.00 μm or less, the amount of the raw material required for forming the second layer is suppressed.

Examples of the metal or alloy forming the third layer include palladium and a palladium alloy. The role of the third layer is to improve the adhesion between the electrical contact material and the mold resin.

The palladium atomic number concentration of the surface layer of the electrical contact material quantified by Auger electron spectroscopy is 50.0% or more. Here, the surface layer of the electrical contact material is the surface layer of the electrical contact material in the portion where the third layer is formed. The palladium atomic number concentration is derived from the palladium component in the third layer.

According to Auger electron spectroscopy, palladium is present at a depth of 10 nm or less from the surface of the surface layer of the electrical contact material and at an atomic number concentration of 50.0% or more. In the present invention, when the concentration of palladium atoms on the surface layer is less than 50%, the adhesion to the mold resin is inferior, a gap is likely to be formed between the mold resin and the electrical contact material, and corrosive gas or the like is likely to enter. .. The above-mentioned palladium atom number concentration is preferably in the range of 60.0% or more and less than 100%, more preferably 65.0% or more and 95.0% or less. When the palladium atom number concentration is in this range, the contact resistance is sufficiently lowered and the adhesion with the mold resin is sufficiently high.

The state of the third layer on the second layer can be determined by the state of palladium obtained by characteristic X-ray energy spectroscopy (SEM-EDX) measurement using a scanning electron microscope. In the SEM-EDX measurement of the surface layer of the electrical contact material, when palladium is present in a speckled dispersed state on the second layer (spotted), a plurality of small layers (island-like layers) having various areas are present. ) Are separated from each other on the second layer (island-like), and the entire surface of the second layer is uniformly covered (solid).

Since palladium has a contact resistance of several mΩ higher than that of silver, the conductivity of the silver component constituting the second layer is carried when the third layer uniformly covers the entire surface of the second layer. It impairs sex. Further, since the third layer exists in a spot shape on the second layer, the surface area of the third layer becomes larger than that in a solid or island-like state, and the electrical contact material and the mold resin can be used. Since the contact area of the electric contact material is increased, the resin adhesion strength of the electric contact material is increased. Therefore, from the viewpoint of contact resistance and resin adhesion, palladium is present in a speckled dispersed state in the SEM-EDX measurement of the surface layer of the electrical contact material, in other words, the silver component of the second layer is partially exposed. It is preferable to do. Palladium existing in a speckled dispersed state in the above SEM-EDX measurement is in a state as shown in FIG. 2 described later.

The average thickness of the third layer is preferably in the range of 0.001 μm or more and 0.100 μm or less, more preferably 0.005 μm or more and 0.050 μm or less. When the average thickness of the third layer is 0.001 μm or more, the above-mentioned effects of contact resistance and adhesion are sufficiently improved. Further, when the average thickness of the third layer is 1.000 μm or less, the amount of the raw material required for forming the third layer is suppressed. The average thickness of the third layer is the thickness of the layer assuming that the third layer is a layer having a uniform thickness over the entire surface of the second layer.

The average thickness of each of the above layers can be measured by a film thickness meter such as a fluorescent X-ray film thickness meter.

Various film forming methods such as plating, clad, vapor deposition, and sputtering can be used for producing the electric contact material, and as a method for easily forming a thin film, at least of the first layer, the second layer, and the third layer. It is preferable to form one layer by an electroplating method, and it is more preferable to form all the first layer, the second layer and the third layer by an electroplating method. The composition of the electroplating solution and the plating conditions can be appropriately determined. In addition, in order to reduce the amount of raw materials used for manufacturing electrical contact materials, single-sided plating in which the first layer, second layer, and third layer are applied only to the switch contact surface side of the electrical contact material, and switch contact surfaces Differential plating, which reduces the plating thickness on the opposite surface, is also an effective means.

The share strength of the electrical contact material with the resin on the surface layer is preferably 8.0 MPa or more. When the share strength is 8.0 MPa or more, the adhesion between the electric contact material and the resin is sufficiently good, and the increase in the contact resistance of the contact portion due to the corrosive gas is suppressed.

The electrical contact material of the present invention is preferably used in any type as long as it is an ordinary contact type electrical contact. In particular, since it is excellent in abrasion resistance and corrosion resistance, the electric contact material of the present invention can be used as a material for electric contacts such as indoor / outdoor sliding contacts for automobiles, reed switches, and camera mount contact switches. It can be used particularly preferably.

According to the embodiment described above, since the electrical contact material has good adhesion to the mold resin, airtightness after resin molding is ensured, and corrosive gas such as sulfurized gas and moisture-rich air invades. Therefore, the long-term reliability of the contact resistance of the contact portion in the switch can be maintained. Further, the electrical contact material has the same contact resistance as the conventional silver-plated electrical contact material.

In the electrical contact material 10 shown in FIG. 1, an example is shown in which the first layer 2 is formed on the entire surface of the conductive substrate 1, but the first layer 2 is formed on at least one surface of the conductive substrate 1. For example, it may be formed only on the upper surface or only the lower surface of the conductive substrate 1.

Further, the third layer 4 may cover the surface of the second layer 3 in a spot-like or island-like state, but in FIG. 1, for simplification, the third layer covers the entire surface of the second layer 3. The electrical contact material 10 that uniformly covers the surface is shown.

Although the embodiments have been described above, the present invention is not limited to the above embodiments, but includes all aspects included in the concept of the present invention and the scope of claims, and varies within the scope of the present invention. Can be modified.

Next, Examples and Comparative Examples will be described, but the present invention is not limited to these Examples.

(Examples 1 to 30 and Comparative Examples 1 to 11)
A conductive substrate of phosphor bronze C52100 having a thickness of 0.05 mm and a width of 50 mm is pretreated under the conditions shown below, and then electroplated under the conditions shown below to obtain the average plating thickness shown in Table 1. The first layer and the second layer were formed on the conductive substrate in this order. Subsequently, the third layer was formed on the second layer so as to have the average plating thickness shown in Table 1 by the electroplating method under the following conditions and the conditions shown in Table 1. In this way, the electrical contact material was obtained. In Comparative Example 11, the third layer was not formed.

For the average plating thickness (coating thickness) of each layer, use a fluorescent X-ray film thickness meter (SFT-9400, manufactured by SII Nanotechnology), set the collimator diameter to 0.1 mm, and set any 10 points on each layer. It was measured and the average value of these measured values was calculated and obtained.

<Pretreatment conditions>
[Cathode electrolytic degreasing]
Solvent degreasing liquid: NaOH 60 g / l
Degreasing conditions: 2.5A / dm ² , temperature 60 ° C, degreasing time 60 seconds [pickling]
Pickling solution: 10% sulfuric acid Pickling conditions: immersion time 30 seconds, room temperature

<Ni plating>
Plating liquid: NiSO ₄ 240 g / L
NiCl ₂ 45g / L
H ₃ BO ₃ 30g / L
Plating conditions: Current density 5A / dm ²
Temperature 50 ℃

<Co plating>
Plating liquid: CoSO ₄ 400 g / L
NaCl 20g / L
H ₃ BO ₃ 40g / L
Plating conditions: Current density 5A / dm ²
Temperature 30 ℃

<NiCo plating>
Plating liquid: HCl 100 g / L
NiCl ₂ 25g / L
CoCl ₂ 25g / L
Plating conditions: Current density 1.2A / dm ²
Temperature 40 ℃

<Ag strike plating>
Plating liquid: AgCN 5 g / L
KCN 60g / L
K ₂ CO ₃ 30g / L
Plating conditions: Current density 2A / dm ²
Temperature 30 ℃

<Ag plating>
Plating liquid: AgCN 50 g / L
KCN 100g / L
K ₂ CO ₃ 30g / L
Plating conditions: Current density 1A / dm ²
Temperature 30 ℃

<Pd plating>
Plating liquid: Pd (NH ₃ ) ₂ Cl ₂ 25-40 g / L
NH ₄ OH 90mL / L
(NH ₄ ) ₂ SO ₄ 50 g / L
Plating conditions: Current density 2-10A / dm ²
Temperature 30 ℃
Stirring conditions: 400-1000 rpm

Ag strike plating and Ag plating were performed in all examples and comparative examples.

In Pd plating, the Pd concentration in the plating bath, the current density, and the stirring speed were controlled in order to adjust the palladium atomic number concentration and the coating state of the third layer. The Pd (NH ₃ ) ₂ Cl ₂ concentration is set to 25 g / L, the palladium atomic number concentration is adjusted to less than 50%, the Pd (NH ₃ ) ₂ Cl ₂ concentration is set to 40 g / L, and the palladium atom number concentration is 50. It was adjusted to% or more and less than 100%. Further, the plating current density is 10 A / dm ² and the stirring speed of the plating solution is 400 rpm to form a speckled third layer, the current density is 2 A / dm ² and the stirring speed is 1000 rpm, and the spots are uniform. A third layer without was formed.

Next, the characteristics and evaluation of the obtained electrical contact material were carried out as follows.

The palladium atomic number concentration was measured by Auger electron spectroscopy as follows. Using an Auger electron spectrophotometer (Mоdel 600, manufactured by ULVAC-PHI), the acceleration voltage is 10 kV and the analysis area is 50 μm at any 5 locations on the surface layer of the electrical contact material where the third layer is formed. Surface qualitative and quantitative analysis was performed at × 50 μm, and the palladium atom number concentration was measured, and the average value of these measured values was taken as the palladium atom number concentration. The results are shown in Table 1. In the measurement of the palladium atomic number concentration, it was standardized so that the total of the elements derived from the electrical contact materials such as Pd, Ag, Ni, Co and C was 100%.

The coating state of the third layer was measured by characteristic X-ray energy spectroscopy (SEM-EDX) using a scanning electron microscope as follows. Using a scanning electron microscope (SEM / EDX) (SEMEDX TypeM, manufactured by Hitachi, Ltd.), an acceleration voltage of 20 kV and observation were performed at any three locations on the surface layer of the electrical contact material in the portion where the third layer was formed. The electron beam was scanned in a region of 10 μm × 10 μm at a magnification of 5000 times, an electron beam spot size of 1 μm, and a measurement depth of 1 μm. In the obtained three Pd EDX mapping images, a 10 μm × 10 μm region was divided into 100 small regions at a 1 μm × 1 μm square, and palladium spots were confirmed among the 100 small regions. We investigated the number of small areas that could be created. Then, when the average value of the number of the small regions in the three mapping images is 5 or more, it is determined to be “presence”, and when it is less than 5, it is determined to be “spotted”.

The contact resistance was measured as follows. Immediately after the formation of the third layer, which is the outermost layer, that is, the electrical contact material immediately after production (before heating), the electrical contact material after the manufactured electrical contact material is allowed to stand in an air bath and heated at 130 ° C. for 90 seconds (heating). For each of the latter), using an Ag probe with a radius of 2 mm, the contact resistance at 10 measurement points was measured with 10 mA energization and a load of 10 gf by the 4-terminal method, and the average value of these measured values was taken as the contact resistance. .. The heating conditions at this time correspond to the heating conditions of the molded resin in the measurement of the resin adhesion strength described later.

The resin adhesion strength (share strength) was measured as follows. Epoxy resin (EME-G630L, Sumitomo Bakelite Co., Ltd.) using a transfer molding machine (Model FTS, manufactured by Kotaki Seiki Co., Ltd.) under the conditions of a mold temperature of 130 ° C., a holding time after molding of 90 seconds, and an injection pressure of 6.865 MPa. A pudding cup-shaped mold resin having ^{a contact area of 10 mm 2} was closely formed on the surface layer of the electrical contact material in the portion where the third layer was formed by injection molding. Five test pieces in which a mold resin was formed on such an electric contact material were produced. Using a bond tester (manufactured by Dage), the electrical contact materials and molds on the five test pieces under the conditions of a load range of 20 kg, a test height of 150 μm, a descent speed of 0.5 μm / s, a test speed of 100 μm / s, and a movement amount of 100 μm. The adhesion strength (share strength) with the resin was measured, and the average value of these measured values was taken as the resin adhesion strength.

Table 1 shows the characteristics and evaluation results of the electrical contact materials measured as described above.

In Examples 1 to 30, it was found that the palladium atom number concentration was in the range of 50% or more and less than 100%, the resin adhesion strength was 8.0 MPa or more, and the resin adhesion was good. Further, as shown in FIG. 2, in the SEM-EDX mapping image of Pd on the surface layer of the electrical contact material of Example 1, it was confirmed that palladium was dispersed in a spot shape. Such spots of palladium could be confirmed in Examples 2 to 16 and 27 to 30 in the same manner. Further, when the palladium atom number concentration is about the same, the resin adhesion strength is higher in Examples 1 to 16 and 27 to 30 in which palladium is spotted than in Examples 17 to 26 in which palladium is not spotted. It was a tendency. In particular, as in Examples 5 to 12, 15, 16, 27, 28, when palladium is present in spots and the palladium atom number concentration is in the range of 60.0% or more and 95.0% or less. The resin adhesion strength was 9.0 MPa or more. Further, as in Examples 1 to 16, palladium is present in spots, the average plating thickness of the first layer is within the range of 0.01 μm or more and 1.00 μm or less, and the average plating thickness of the second layer is 0.01 μm. When the average plating thickness of the third layer is within the range of 0.001 μm or more and 0.100 μm or less within the range of 1.00 μm or less, the contact resistance before and after heating is 3.0 mΩ or less and the resin adheres to each other. The strength was excellent.

On the other hand, in Comparative Examples 1 to 11, the palladium atom number concentration was less than 50%, and the amount of Pd in the third layer, which is the outermost layer of the electrical contact material, was small, so that the resin adhesion strength was less than 8.0 MPa. It was found that the resin adhesion was inferior.

1 Conductive substrate 2 1st layer 3 2nd layer 4 3rd layer 10 Electrical contact material

Claims (7)

A conductive substrate containing copper, a first layer containing nickel or cobalt formed on at least one surface of the conductive substrate, a second layer containing silver formed on the first layer, and the second layer. and a third layer containing palladium which is formed in the upper state, and are palladium atomic concentration of the surface layer to be quantified more than 50.0% by Auger electron spectroscopy,
An electrical contact material characterized in that palladium is present in a speckled dispersed state in the SEM-EDX measurement of the surface layer. A conductive substrate containing copper, a first layer containing nickel or cobalt formed on at least one surface of the conductive substrate, a second layer containing silver formed on the first layer, and the second layer. It has a third layer containing palladium formed on it, and the concentration of palladium atoms in the surface layer quantified by Auger electron spectroscopy is 50.0% or more.
An electrical contact material characterized by having a share strength of the surface layer with a resin of 8.0 MPa or more. A conductive substrate containing copper, a first layer containing nickel or cobalt formed on at least one surface of the conductive substrate, a second layer containing silver formed on the first layer, and the second layer. It has a third layer containing palladium formed on it, and the concentration of palladium atoms on the surface layer quantified by Auger electron spectroscopy is 50.0% or more.
In the SEM-EDX measurement of the surface layer, palladium was present in a speckled dispersed state.
An electrical contact material characterized by having a share strength of the surface layer with a resin of 8.0 MPa or more. The electrical contact material according to any one of claims 1 to 3, wherein the average thickness of the third layer is in the range of 0.001 μm or more and 0.100 μm or less. The electrical contact material according to any one of claims 1 to 4 , wherein the average thickness of the second layer is in the range of 0.01 μm or more and 1.00 μm or less. The electrical contact material according to any one of claims 1 to 5 , wherein the average thickness of the first layer is in the range of 0.01 μm or more and 1.00 μm or less. A switch using the electrical contact material according to any one of claims 1 to 6.

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