JP2010242117A - Electrical contact and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrical contact which prevents stress corrosion particularly because of having a plated layer with a reduced residual stress formed thereon, is superior in corrosion resistance and is stable in its performance. <P>SOLUTION: The plated layer is formed by stacked plated films of a tensile-stress plated layer 3a and a compressive-stress plated layer 3b, to constitute an underlayer 3 or a precious metal layer 4. Further, a plated structure is formed by stacking a plurality of the tensile-stress plated layers 3a and the compressive-stress plated layers 3b. Thereby, the plated layer having the reduced residual stress inside the plated layer is obtained, and the residual stress can be removed by heat-treating the plated layer. The tensile-stress plated layer and the compressive-stress plated layer can be formed by varying a type of a plating bath to be used in plating treatment, a type of a brightener to be added to the plating bath or a current density during the plating treatment. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to electrical contacts such as switches and connectors in which a base layer and a noble metal layer are laminated and plated on a base material.

  Conventionally, in an electrical contact having a noble metal film such as Au or Ag on the surface of a base material, Ni (nickel) or alloy plating containing Ni has been used as a base for the noble metal film. In the past, electrical contacts were formed by high-speed plating in order to improve productivity. At this time, high-speed plating could be promoted by increasing the current density during plating, and the grain size of the precipitated crystal grains could be reduced, thereby forming a dense plating film.

JP 2005-248269 A

  As described above, in electrolytic plating, a dense plating film can be obtained when the current density is increased, but the residual stress (internal stress) in the plating film increases, which causes poor plating adhesion and causes peeling of the plating. The problem is that the residual stress is released due to changes over time, causing corrosion and discoloration failure called stress corrosion.

  Patent Document 1 discloses that the electrodeposition stress of the Ni plating film can be reduced by using a watt bath or a sulfamine bath, but it does not eliminate the residual stress during plating.

  Accordingly, the present invention solves the above-described conventional problems, and in particular, an electrical contact that can effectively reduce the residual stress inside the plating layer and ensure good adhesion, and the manufacture thereof, compared to the prior art. It aims to provide a method.

The present invention is an electrical contact comprising a plating layer formed by plating on a base material,
The plating layer is formed of a laminated plating film including at least one tensile stress plating layer and a compressive stress plating layer.

  As a result, the residual stress (internal stress) of the entire plating layer can be offset between the tensile stress plating layer and the compressive stress plating layer, and can be reduced appropriately and easily, and electrical contacts with excellent plating adhesion, corrosion resistance, etc. It can be.

  Moreover, it is preferable that the said multilayer plating film is heat-processed. The residual stress in the individual layers of the tensile stress plating layer and the compressive stress plating layer can be reduced, and the residual stress inside the plating layer can be brought closer to zero more effectively.

  In the present invention, the base layer is formed by plating on the base material, and a noble metal layer in which a noble metal is plated on the surface of the base layer, and the base layer is formed by the multilayer plating film. It is preferable. This improves the adhesion between the base layer and the base material, and between the base layer and the noble metal layer, and also prevents cavitation and precipitation inside the plating based on the elution of the base layer and has excellent corrosion resistance. Can be. In the present invention, it is preferable that the underlayer is formed of Ni or an alloy containing Ni. It has been confirmed that good adhesion and corrosion resistance can also be obtained in experiments to be described later.

Further, the present invention provides a method for producing an electrical contact comprising a plating layer formed by plating on a base material.
The plating layer is formed of a multilayer plating film in which at least one tensile stress plating layer and at least one compression stress plating layer are stacked.

  Thereby, the residual stress inside the plating layer can be offset between the tensile stress plating layer and the compression stress plating layer, and can be appropriately and easily reduced, and an electrical contact excellent in plating adhesion and corrosion resistance can be manufactured. In addition, according to the method for producing an electrical contact of the present invention, even if the current density at the time of plating is increased, the residual stress inside the plating layer can be reduced as compared with the conventional case, so that high-speed plating is possible, and productivity is improved and electricity is improved. Contacts can be manufactured.

  In the electrical contact manufacturing method of the present invention, the tensile stress plating layer and the compression stress plating layer can be laminated by changing the type of brightener in the plating bath.

  Or in the manufacturing method of the electrical contact of this invention, the current density in a plating bath can be changed and a tensile stress plating layer and a compression stress plating layer can be laminated | stacked. Thereby, the tensile stress plating layer and the compression stress plating layer can be laminated without changing the plating bath.

  Furthermore, it is preferable to heat-treat after laminating the tensile stress plating layer and the compressive stress plating layer.

  Further, in the present invention, a base layer plated on the base material and a noble metal layer plated with a noble metal on the surface of the base layer are formed, and the base layer is formed of the multilayer plating film. It is preferable to do.

  The electrical contact of the present invention can appropriately and easily reduce the residual stress inside the plating layer, and can improve the plating adhesion and corrosion resistance. Further, in the method for manufacturing an electrical contact according to the present invention, even if the current density during plating is increased, the residual stress can be reduced as compared with the conventional method, so that high-speed plating is possible, and the electrical contact is manufactured with improved productivity. be able to.

Sectional drawing of the electrical contact of 1st Embodiment, Sectional drawing of the electrical contact of 2nd Embodiment, A graph showing the difference in stress inside the plating depending on the type of brightener and plating bath, SEM photograph showing the state of Ni plating in Comparative Example 1,

  FIG. 1 is a sectional view of an electrical contact according to the first embodiment of the present invention, and FIG. 2 is a partial sectional view of the electrical contact according to the second embodiment of the present invention.

  An electrical contact 1 shown in FIG. 1 includes a base material 2, a base layer 3 plated on the surface of the base material 2, and a noble metal layer 4 plated on the surface of the base layer 3.

  As shown in FIG. 1, the electrical contact of the first embodiment is a multilayer plating film in which the underlayer 3 is composed of a tensile stress plating layer 3a and a compressive stress plating layer 3b plated on the surface thereof. As long as the tensile stress plating layer 3a and the compression stress plating layer 3b are laminated, the underlayer 3 may be a laminated plating film in which the tensile stress plating layer 3a is laminated on the surface of the compression stress plating layer 3b.

  A tensile stress acts inside the tensile stress plating layer 3a, and a compressive stress acts inside the compressive stress plating layer 3b. Since the tensile stress and the compressive stress are forces acting in opposite directions, when the tensile stress plating layer 3a and the compressive stress plating layer 3b are laminated, the stress is canceled between these plating layers, and the entire underlayer 3 is formed. Residual stress (internal stress) can be reduced, more preferably zero. As a result, stress corrosion over time of the underlayer 3 can be effectively prevented, the adhesion with the noble metal layer 4 plated on the surface of the underlayer 3 and the adhesion with the base material 2 can be improved, and a stable contact A long-life electrical contact with properties is obtained.

  Therefore, as shown in FIG. 1, when the tensile stress plating layer 3a and the compressive stress plating layer 3b are provided one by one, the tensile stress of the tensile stress plating layer 3a and the compressive stress of the compressive stress plating layer 3b The absolute values are preferably equal or nearly equal. When the absolute values of the stress are equal, the stress in the layer is completely canceled when the tensile stress plating layer 3a and the compression stress plating layer 3b are laminated, and the stress of the underlayer 3 becomes zero. Even when the absolute values of the stresses are almost equal, the stress inside the layer is almost canceled out, so that the stress of the underlayer 3 can be made substantially zero.

  For example, when the tensile stress plating layer 3a and the compressive stress plating layer 3b are formed of the same material, the tensile stress can be changed by changing the current density of the plating bath or changing the type of brightener added to the plating bath. Alternatively, it can be adjusted to either compressive stress. The stress value can be changed depending on the type of plating bath, the strength of current density, the plating thickness, and the like.

  The base material 2 is formed of a highly conductive metal, and for example, brass or phosphor bronze is preferably used.

  The tensile stress plating layer 3a or the compressive stress plating layer 3b that forms the base layer 3 is not particularly limited as long as it is a metal or metal alloy that forms the plating layer, but a metal such as Ni, Sn, Zn, Cu, or the like. An alloy containing a metal is preferably used. For example, Ni or a Ni alloy is particularly preferably used. The tensile stress plating layer 3a and the compressive stress plating layer 3b are preferably formed of the same metal or metal alloy, but may be formed of different metals or metal alloys. The noble metal layer 4 is preferably made of a noble metal such as Au or Ag.

  For example, the film thickness of the underlayer 3 can be 1 to 2 μm, and the film thickness of the noble metal layer 4 can be 0.2 to 0.4 μm. In this case, the tensile stress plating layer 3a and the compressive stress plating layer 3b that form the base layer 3 are each formed with substantially the same film thickness as 0.5 to 1 μm, but the film thickness may be different.

  In the electrical contact 1 shown in FIG. 1, the layer formed on the surface side of the tensile stress plating layer 3a and the compressive stress plating layer 3b may be formed of a noble metal.

  For example, the tensile stress plating layer 3a is formed of a metal or metal alloy such as Ni, Sn, Zn, or Cu, the compressive stress plating layer 3b is formed of a noble metal such as Au or Ag, and is further formed on the surface of the compressive stress plating layer 3b. The noble metal layer 4 can be plated. Also in this case, the residual stress is offset between the tensile stress plating layer 3a and the compression stress plating layer 3b, and the residual stress inside the plating layer becomes zero or almost zero. Since the tensile stress plating layer 3b is formed by plating with a noble metal, an electrical contact can be obtained even if the noble metal layer 4 is not formed on the surface.

  Furthermore, although not shown in the drawing, the compression stress plating layer 3b is plated on the surface of the base material 2, and the tensile stress plating layer 3a is plated on the surface of the compression stress plating layer 3b, and the lamination of the tensile stress plating layer 3a and the compression stress plating layer 3b. When the order is the reverse of FIG. 1, the compressive stress plating layer 3b is formed of a metal or metal alloy such as Ni, Sn, Zn, or Cu, and the tensile stress plating layer 3a is formed of a noble metal such as Au or Ag. You can also. In this case, the noble metal layer 4 may or may not be plated on the surface of the tensile stress plating layer 3a.

  Further, for example, both the tensile stress plating layer 3a and the compression stress plating layer 3b can be formed by plating with a noble metal such as Au or Ag. In this case, the noble metal layer 4 may be plated on the surface of the compressive stress plating layer 3b, or the noble metal layer 4 may not be plated. Further, another metal or metal alloy plating layer may be formed between the base material 2 and the tensile stress plating layer 3a. Even when both the tensile stress plating layer 3a and the compression stress plating layer 3b are formed by plating with a noble metal such as Au or Ag, the surface of the base material 2 is plated with the compression stress plating layer 3b, and the compression stress plating layer 3b. A multilayer plating film in which a tensile stress plating layer 3a is plated on the surface of the film may be used.

  That is, if the tensile stress plating layer 3a or the compressive stress plating layer 3b is a plating layer in which a tensile stress or a compressive stress works, the residual stress inside the plating layer is offset when the layers are stacked, so that There is no limitation, and not only metals such as Ni, Sn, Zn, and Cu, or metals such as these, but also metals such as Au or Ag are preferably used. Moreover, there is no restriction | limiting also in the lamination | stacking order of the tensile stress plating layer 3a and the compression stress plating layer 3b.

  However, as shown in FIG. 1, in a configuration in which a base layer 3 of Ni or Ni alloy is formed on a base material 2 and a noble metal layer 4 such as Au or Ag is laminated, the base layer 3 is formed on the noble metal layer 4. As compared with this, the rigidity (hardness) is high, and as a result, residual stress is likely to be accumulated in the underlayer 3, so that the underlayer 3 is laminated with a tensile stress plating layer 3a and a compressive stress plating layer 3b as shown in FIG. It is preferable to use a film because the residual stress can be reduced more effectively.

  The electrical contact 1 is preferably further heat-treated. For example, after the base layer 3 is plated, or after the base layer 3 and the noble metal layer 4 are plated, the residual of the tensile stress plating layer 3a and the compressive stress plating layer 3b constituting the base layer 3 are retained. The stress can be brought close to zero, and the residual stress of the entire underlayer 3 can be brought closer to zero (preferably can be made zero) more effectively. The heat treatment is preferably performed at a temperature of 80 ° C. or higher and lower than 300 ° C. If the heat treatment temperature is lower than 80 ° C., the residual stress cannot be completely relaxed, and if it is about 300 ° C. or higher, the coarsening of the crystal grains is promoted, and between the underlayer 3 and the base material 2, and Since a diffusion reaction between the underlayer 3 and the noble metal layer 4 is likely to occur, neither is preferable. The heat treatment is preferably performed in an inert gas atmosphere.

  The electrical contact 5 of the second embodiment shown in FIG. 2 includes a base material 2, a base layer 3 plated on the surface of the base material 2, and a noble metal layer 4 plated on the surface of the base layer 3. 1 is the same as the electrical contact 1 shown in FIG. 1, but the underlayer 3 is configured by alternately laminating a plurality of tensile stress plating layers 3a and compressive stress plating layers 3b.

  Also in the electrical contact 5 of FIG. 2, the tensile stress plating layer 3a and the compressive stress plating layer 3b are laminated, and the stress is canceled between these plating layers. Or nearly equal to zero. As a result, stress corrosion over time of the underlayer 3 can be effectively prevented, the adhesion with the noble metal layer 4 plated on the surface of the underlayer 3 and the adhesion with the base material 2 can be improved, and the stable contact A long-life electrical contact with properties is obtained. In addition, as shown in FIG. 2, a plurality of tensile stress plating layers 3a and compressive stress plating layers 3b are alternately stacked, so that each of the tensile stress plating layers 3a and the compressive stress plating layers 3b is more sufficiently than conventional. It is easy to finely adjust the residual stress of the entire underlayer 3 while forming it thin and reducing the film thickness of the entire underlayer 3.

  The electrical contact 5 shown in FIG. 2 is also not particularly limited in the stacking order of the tensile stress plating layer 3a and the compressive stress plating layer 3b. The compressive stress plating layer 3b is plated on the surface of the base material 2, and the surface of the compressive stress plating layer 3b. The tensile stress plating layer 3a is plated, and the compressive stress plating layer 3b and the tensile stress plating layer 3a can be alternately stacked.

  For example, in FIG. 2, three layers of the tensile stress plating layer 3a and the compression stress plating layer 3b are alternately laminated, but if there are a plurality of the tensile stress plating layers 3a and a plurality of the compression stress plating layers 3b, the number thereof is increased. There is no particular limitation. The tensile stress plating layer 3a and the compressive stress plating layer 3b are preferably laminated alternately. However, the tensile stress plating layer 3a is formed on the surface of the tensile stress plating layer 3a or the compressive stress is applied on the surface of the compression stress plating layer 3b. The plating layer 3b may be laminated. When a plurality of tensile stress plating layers 3a and compression stress plating layers 3b are alternately laminated, the number of plating layers is preferably the same. However, any of the tensile stress plating layer 3a and the compressive stress plating layer 3b may be smaller than the other plating layers.

  When the tensile stress plating layer 3a and the compressive stress plating layer 3b are the same number, the tensile stress of the tensile stress plating layer 3a and the compressive stress of the compressive stress plating layer 3b are equal or nearly equal to each other. It is preferable. When the absolute value of each stress is equal, when a plurality of tensile stress plating layers 3a and compressive stress plating layers 3b are stacked, the stress inside the layers is completely offset, and the residual stress of the underlayer 3 becomes zero. When the absolute values of the respective stresses are substantially equal, the stress inside the layer is almost canceled out, so that the residual stress of the underlayer 3 can be made substantially zero.

  In addition, similar to the electrical contact 1 of FIG. 1, the base material 2 is formed of a highly conductive metal such as brass or phosphor bronze. The noble metal layer 4 is preferably made of a noble metal such as Au or Ag. As the tensile stress plating layer 3a or the compression stress plating layer 3b, a metal or a metal alloy such as Ni, Sn, Zn, or Cu that can form a plating layer is preferably used. Alternatively, some of the plurality of tensile stress plating layers 3a or compressive stress plating layers 3b may be formed of a noble metal such as Au or Ag. In addition, when the tensile stress plating layer 3a or the compressive stress plating layer 3b formed on the uppermost side is formed of a noble metal such as Au or Ag, the noble metal layer 4 may not be formed.

  For example, the film thickness of the underlayer 3 can be 0.6 to 1 μm, and the film thickness of the noble metal layer 4 can be 0.2 to 0.4 μm. The tensile stress plating layer 3a and the compressive stress plating layer 3b that form the base layer 3 are formed with a total thickness of 0.3 to 0.5 μm, which is thinner than the electrical contact 1 of FIG. The tensile stress plating layer 3a and the compressive stress plating layer 3b are formed with substantially the same film thickness, but the tensile stress plating layer 3a and the compression stress plating layer 3b may have different film thicknesses.

  It is preferable that the electrical contact 5 of the second embodiment shown in FIG. By the heat treatment, the residual stress of each of the tensile stress plating layer 3a and the compressive stress plating layer 3b can be brought close to zero, and the residual stress of the entire underlayer 3 can be brought closer to zero (preferably zero). Can be). The heat treatment is preferably performed at a temperature of 80 ° C. or higher and lower than 300 ° C. If the heat treatment temperature is lower than 80 ° C., the residual stress cannot be completely relaxed, and if it is 300 ° C. or higher, the coarsening of crystal grains is promoted, and between the underlayer 3 and the base material 2 and below Since diffusion reaction between the formation 3 and the noble metal layer 4 is likely to occur, neither is preferable. The heat treatment is preferably performed in an inert gas atmosphere.

  In the embodiment shown in FIGS. 1 and 2, the tensile stress plating layer 3a and the compressive stress plating layer 3b have the same number of layers, but may have different numbers of layers. In such a case, the absolute value of the stress of each plating layer with the smaller number of layers is made larger than the absolute value of the stress of each plating layer with the larger number of layers so that the residual stress inside the plating layer approaches zero. It is preferable to adjust.

  A method of manufacturing the electrical contacts 1 and 5 according to the first and second embodiments shown in FIGS. 1 and 2 will be described.

  In the electrical contact 1 of the first embodiment, the tensile stress plating layer 3a is formed on the base material 2, and the compressive stress plating layer 3b is formed on the tensile stress plating layer 3a. Further, the noble metal layer 4 is formed by plating on the compressive stress plating layer 3b. The plating may be either electrolytic plating or electroless plating.

  Alternatively, the compressive stress plating layer 3b may be formed on the base material 2, the tensile stress plating layer 3a may be further formed, and the noble metal layer 4 may be formed by plating on the tensile stress plating layer 3a. In this case, the plating may be either electrolytic plating or electroless plating.

  For example, the base layer 3 is plated with a thickness of 1 to 2 μm, and the noble metal layer 4 is plated with a thickness of 0.2 to 0.4 μm.

  In the electrical contact 5 of the second embodiment, the tensile stress plating layer 3a is formed on the base material 2, the compression stress plating layer 3b is formed on the tensile stress plating layer 3a, and then the tensile stress plating layer 3a and The plating formation of the compressive stress plating layer 3b is repeated. And the noble metal layer 4 is plated on the outermost surface. In this case as well, the compressive stress plating layer 3b may be formed on the base material 2, the tensile stress plating layer 3a may be further plated, and these may be repeated, and the noble metal layer 4 may be plated on the outermost surface.

  FIG. 3 shows plating residual stress when Ni metal is electroplated by changing the plating bath, the type of brightener added to the plating bath, and the plating thickness.

The experiment was conducted on the surface of the copper plate as a base material when the adsorption type brightener and the eutectoid type brightener were added to the Watt bath or the sulfamine bath, respectively, and when no brightener was added. This was performed by electroplating Ni with a thickness and measuring the strain of the plated base material. When the residual stress shows a positive value, tensile stress acts inside the plating, and when it shows a negative value, compressive stress works. The plating was carried out at a plating bath temperature of 50 ° C. and a current density of 20 A / dm ² . The adsorption type brightener is, for example, coumarin, and the eutectoid type brightener is, for example, saccharin or sodium naphthalene sulfonate.

  As shown in FIG. 3, when a eutectoid type brightener is added, compressive stress acts inside both the Watt bath and the sulfamine bath, and there is no significant difference in the value of the stress caused by the type of bath. When no brightener is added, or when an adsorption-type brightener is added, tensile stress acts inside the watt bath and sulfamine bath, and the watt bath uses the watt bath compared to plating in the sulfamine bath. The value of tensile stress is large.

  From the graph of FIG. 3, a plating bath 1 containing an adsorption type brightener in a plating bath containing Ni ions, or a plating bath-1 not containing a brightener, and a eutectoid type brightener in a plating bath containing Ni ions. If the Ni layer is alternately laminated using the plating bath-1 and the plating bath-2, the tensile stress plating layer and the compression stress plating layer can be appropriately and easily formed. Multi-layer plating can be performed.

  In addition, plating when adding a eutectoid type brightener is applied to both the Watt bath and the sulfamine bath, when the adsorption type brightener is added to the sulfamine bath, or when no brightener is added. The values are almost equal. Therefore, when the underlying layer 3 is formed of Ni and the same number of the tensile stress plating layer 3a and the compressive stress plating layer 3b are laminated, the tensile stress plating layer 3a is formed with a sulfamine bath (no brightener added) or sulfamine. If the plating film formed by adding an adsorption type brightener to the bath and the plating film formed by adding the eutectoid type brightener to the compression stress plating layer 3b, the residual stress of the entire underlayer 3 is zero. Or it can be almost zero.

  Moreover, each of the tensile stress plating layer 3a and the compressive stress plating layer 3b can be obtained also by the current density of the plating bath. Therefore, if the current density for obtaining the tensile stress plating layer and the current density for obtaining the compression stress plating layer are alternately changed using the same plating bath, the tensile stress plating layer 3a and the compression stress plating layer 3b Can be laminated and plated. In this manufacturing method, in order to obtain the tensile stress plating layer 3a and the compression stress plating layer 3b, it is not necessary to change the bath, and a simple manufacturing method can be realized.

  It is preferable to heat-treat after laminating the underlayer 3 and the noble metal layer 4 or after plating the underlayer 3. The heat treatment is preferably performed at a temperature of 80 ° C. or higher and lower than 300 ° C. If the heat treatment temperature is lower than 80 ° C., the residual stress cannot be completely relaxed, and if it is about 300 ° C. or higher, the coarsening of the crystal grains is promoted, and between the underlayer 3 and the base material 2, and Since a diffusion reaction between the underlayer 3 and the noble metal layer 4 is likely to occur, neither is preferable. The heat treatment is preferably performed in an inert gas atmosphere.

  As described above, the residual stress of the entire base layer 3 can be made zero or almost zero easily and appropriately, and the base layer 3 and the base material 2 and the base layer 3 and the noble metal layer 4 can be formed with good adhesion. Can do. In addition, the electrical contact manufacturing method of the present embodiment can reduce the residual stress inside the plating layer compared to the conventional case even if the current density during plating is increased, thereby enabling high-speed plating, improving productivity, and Contacts can be manufactured.

An electrical contact shown in FIG. 1 was prepared using Ni metal plating as the underlayer 3 and a corrosion resistance test was performed.
Example 1
Brass is used as the base material 2, Ni is plated on the surface of the base material 2 using 1 type of Ni plating baths A and B, respectively, to form the base layer 3, and Au is further plated on the surface of the base layer 3 to 0.2 μm. As a result, an electrical contact having a plated laminated structure shown in FIG. 1 was obtained.

Here, the Ni plating bath A includes nickel sulfamate 300 g / L, boric acid 30 g / L, nickel chloride 10 g / L, and coumarin 0.005 mol / L. By using this Ni plating bath A, tensile stress plating is performed. Layer 3a was obtained. The Ni plating bath B includes nickel sulfamate 300 g / L, boric acid 30 g / L, nickel chloride 10 g / L, and sodium naphthalene sulfonate 3 g / L. By using this Ni plating bath B, the compression stress plating layer 3b is formed. Obtained. Ni plating baths A and B were 50 ° C., and Ni plating was performed at a current density of 10 A / dm ² .

(Example 2)
The electrical contact of Example 1 was further heat-treated at a temperature of 200 ° C. for 30 minutes.

(Comparative Example 1)
Brass was used as the base material 2, Ni was plated on the surface of the base material 2 using Ni plating bath B, and Ni was plated by 2 μm to form the base layer 3. Further, Au was plated on the surface of the base layer 3 by 0.2 μm. Here, Ni plating bath B has the same composition as Ni plating bath B used in Example 1, and Ni plating was performed with the same bath temperature and current density as in Example 1.

  For these electrical contacts of Example 1, Example 2, and Comparative Example 1, two types of corrosion resistance tests, a moisture resistance test and a nitric acid aeration test, were performed.

  The moisture resistance test was performed by leaving each electrical contact for 120 hours in a temperature of 85 ° C. and a humidity of 95% RH, and the state of the electrical contact after being left was observed.

  The nitric acid aeration test was performed by sealing each electrical contact with 50 ml of concentrated nitric acid in a desiccator and exposing for 1 hour, and the state of the electrical contact after exposure was observed.

(Results of corrosion resistance test)
The electrical contact of Comparative Example 1 had plating peeling after the moisture resistance test. FIG. 4 is an SEM photograph of a cross section of the electrical contact in Comparative Example 1. As shown in FIG. 4, it was found that Ni was eluted, Ni was deposited on the surface, and the inside was hollow. In the electrical contact after the nitric acid aeration test, a blue product was formed so as to cover most of the Au plating surface.

  In the electrical contact of Example 1, plating peeling did not occur after the moisture resistance test. No peeling was confirmed even by cross-sectional SEM observation. Moreover, in the electrical contact after the nitric acid aeration test, it was recognized that a blue product was generated in spots on the Au plating surface, but most of the surface remained as Au plating.

  In the electrical contact of Example 2, plating peeling did not occur after the moisture resistance test. No peeling was confirmed even by cross-sectional SEM observation. In addition, no change was observed on the Au plating surface even at the electrical contact after the nitric acid aeration test.

  As described above, stress corrosion occurred in Comparative Example 1 in which the Ni underlayer is composed of only one layer (one compression stress plating layer). However, stress corrosion due to aging occurred in the electrical contacts of Examples 1 and 2. You can see that they are not. This is presumably because the residual stress of the entire underlayer was made zero or almost zero by forming the Ni underlayer by laminating the tensile stress plating layer and the compressive stress plating layer.

1, 5 Electric contact 2 Base material 3 Underlayer 3a Tensile stress plating layer 3b Compressive stress plating layer 4 Noble metal layer

Claims (9)

In an electrical contact provided with a plating layer formed by plating on a base material,
The electrical contact, wherein the plating layer is formed of a laminated plating film including at least one tensile stress plating layer and a compressive stress plating layer.   The electrical contact according to claim 1, wherein the multilayer plating film is heat-treated.   The underlayer formed by plating on the base material and a noble metal layer obtained by plating a noble metal on the surface of the underlayer, and the underlayer is formed of the multilayer plating film. 2. The electrical contact according to 2.   The electrical contact according to claim 3, wherein the underlayer is formed of Ni or an alloy containing Ni. In a method for producing an electrical contact comprising a plating layer formed by plating on a base material,
The method of manufacturing an electrical contact, wherein the plating layer is formed of a laminated plating film in which at least one tensile stress plating layer and compressive stress plating layer are laminated.   6. The method for producing an electrical contact according to claim 5, wherein the tensile stress plating layer and the compressive stress plating layer are laminated by changing the type of the brightener in the plating bath.   The method for producing an electrical contact according to claim 5, wherein the tensile stress plating layer and the compressive stress plating layer are laminated while changing the current density in the plating bath.   The method for manufacturing an electrical contact according to claim 5, wherein heat treatment is performed after the tensile stress plating layer and the compressive stress plating layer are laminated.   6. An underlayer formed by plating on the base material and a noble metal layer in which a noble metal is plated on the surface of the underlayer, and the underlayer is formed of the laminated plating film. 9. The method for producing an electrical contact according to any one of 8 above.

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