JP5210907B2 - Manufacturing method of electrical contacts - Google Patents

Description

  The present invention relates to a method for manufacturing an electrical contact in which a noble metal plating film is plated on the surface of a switch, a connector or the like.

  Conventionally, chemically stable Au has been used on the surface of the electrical contact. For example, the electrical contact is formed of a laminated structure in which the surface of a base metal made of copper is plated with Au via Ni plating. The reason why Ni plating is required is to suppress the diffusion phenomenon between Au and the base metal.

JP-A-2005-19335 JP 2007-217798 A

  By the way, if the plating thickness of the Ni plating is increased, the effect of preventing the base material diffusion can be enhanced. However, problems such as waste of manufacturing cost and worsening of post-workability and easy occurrence of cracks occur. It was.

  On the other hand, if the plating thickness of the Ni plating is reduced, the manufacturing cost can be reduced and the post-workability can be improved, but there is a problem that it is easily corroded due to the pinhole generated in the Ni plating. occured.

  The above-mentioned patent documents do not recognize the above-described conventional problems, and naturally, means for solving them is not shown.

  Accordingly, the present invention is for solving the above-described conventional problems, and in particular, a noble metal plating film can be deposited in a pinhole formed in a base plating film of Ni or a Ni alloy and appropriately sealed. It aims at providing the manufacturing method of an electrical contact.

The method of manufacturing an electrical contact in the present invention is characterized by having the following steps.
(A) a step of plating a base plating film of Ni or Ni alloy by electrolytic plating on a base metal;
(B) A noble metal plating film made of a platinum group or a platinum group alloy is formed by electroplating on the surface of the base plating film. At this time, the current density is increased and the initial plating is performed. The process of lowering and plating the rest.

  When the noble metal plating film is formed by plating as described above, it can be microcrystallized by first setting a high current density. For this reason, a microcrystalline noble metal plating film can be deposited in the pinhole generated by thinly forming the base plating film made of Ni or Ni alloy, and can be effectively sealed. Since the pinhole is an active point of plating and is preferentially deposited in the pinhole, the noble metal plating film may be formed by plating for a short initial time, for example, with a higher current density than usual. Further, when a noble metal is formed by plating, a brightening agent is usually contained in the plating tank. However, if the current density is high, a large amount of the brightening agent is contained in the plating film. However, when a large amount of brightener is deposited on the surface of the noble metal plating film, the contact performance and the adhesion when further plating is performed on the surface of the noble metal plating film are deteriorated. For this reason, when plating a noble metal plating film, the current density is not high from the beginning to the end. It is possible to reduce the amount of the brightener deposited on the surface of the film and improve the contact performance and adhesion.

  In the present invention, in the step (b), the noble metal plating film is preferably formed by plating with a platinum group or a platinum group alloy. Thereby, base material diffusion can be more effectively suppressed.

  In the present invention, after plating the noble metal plating film made of platinum group or platinum group alloy, Au plating or Ag plating can be applied to the surface of the noble metal plating film. In the present invention, a noble metal plating film made of a platinum group or a platinum group alloy can be formed on the contact surface, or as described above, even when Au plating or Ag plating is further performed, Au plating and Ag plating are formed thinner than conventional ones. I can do it.

  According to the method for producing an electrical contact of the present invention, a noble metal plating film can be deposited in a pinhole formed in a base plating film of Ni or Ni alloy and appropriately sealed.

Sectional drawing which shows the manufacturing process of the electrical contact of this embodiment, Partial plan view of a base material substrate (hoop material) having a region for forming electrical contacts, Schematic showing the arrangement of the anode in the plating tank, Schematic showing the arrangement in the plating tank where the mask plate is arranged, FIG. 4 is a plan view of the mask plate in FIG. Schematic which shows arrangement | positioning of the anode in a plating tank.

  FIG. 1 is a process diagram showing a method of manufacturing an electrical contact according to the present embodiment, and each figure is a cross-sectional view during the manufacturing process.

  In the step shown in FIG. 1A, a base plating film 2 made of Ni or Ni alloy is formed on the surface 1a of the base metal 1 by electroplating. The base metal 1 is Cu, brass or the like. The Ni alloy constituting the base plating film 2 is NiCo or the like.

  In the step of FIG. 1A, the plating thickness H1 of the base plating film 2 is formed as thin as about 0.02 to 1 μm. At this time, a large number of pinholes 2 a are formed in the base plating film 2. The hole diameter of the pinhole 2a is about several nm to 1 μm. The particle diameter of the crystal grains of the base plating film 2 is about several tens nm to several hundreds nm.

  Next, in the step shown in FIG. 1B, the noble metal plating film 3 is formed on the surface of the base plating film 2 by electrolytic plating. The noble metal plating film 3 is made of one or more of Au, Ag, Pt, Pd, Rh, Ir, Ru, and Os, or an alloy (inorganic compound) containing the noble metal and an element other than the noble metal. Form with. At this time, for example, the initial current density is set to be higher than the normal current density, and the initial plating film 3a having fine crystal grains is formed by plating. FIG. 1B schematically shows that the crystal grains are fine and preferentially precipitate in the pinholes 2 a of the base plating film 2. The crystal grain size of the initial plating film 3a is about 0.1 nm to several tens of nm. The plating thickness of the initial plating film 3a is about 0.0001 to 0.1 μm.

  The initial plating film 3a is formed by plating in a state where the current density is increased for the first short time (about several seconds). The pinhole 2a formed in the base plating film 2 as shown in FIG. 1B is an active point when the noble metal plating film 3 is formed by plating, and fine crystal grains are preferentially given by increasing the current density. Precipitates in the pinhole 2a.

  Next, in the step of FIG. 1C, after the initial plating film 3a is formed by plating, the current density is returned to, for example, a normal current density (lower than the current density at the time of forming the initial plating film 3a), and the rest The plating film 3b is formed by electroplating. In the embodiment of FIG. 1, the noble metal plating film 3 is constituted by the initial plating film 3a and the remaining plating film 3b.

  The remaining plating film 3b has a crystal grain size larger than that of the initial plating film 3a in order to perform plating with a reduced current density. The particle diameter of the crystal grains of the remaining plating film 3b is about several tens nm to several hundreds nm. The remaining plating film b can be arbitrarily formed by a necessary plating thickness. As an example, the plating thickness of the remaining plating film 3b is about 0.05 μm.

  Thus, when the noble metal plating film 3 is formed by plating, first, the microcrystalline initial plating film 3a is preferentially deposited in the pinhole 2a, so that the noble metal plating film 3 is appropriately formed on the base plating film 2. The pinhole 2a thus formed can be sealed.

  By the way, it is not preferable to form the noble metal plating film 3 with a higher current density than usual from the beginning to the end for the following reason.

  When the noble metal plating film 3 is formed by electroplating, a brightening agent is usually contained in the plating tank. The brighter is more easily contained in the plating film as the current density is increased. Moreover, the particle diameter of crystal grains can be reduced by increasing the amount of brightener. That is, when the initial plating film 3a of the noble metal plating film 3 is formed by plating, by setting the current density high, the amount of brightener contained in the initial plating film 3a increases and the particle diameter of the crystal grains decreases. Therefore, when the noble metal plating film 3 is formed by plating at a high current density from the beginning to the end, a large amount of brightener is deposited on the surface of the noble metal plating film 3.

  However, when a large amount of brightener is deposited on the surface, the contact performance as a contact is lowered. Alternatively, as shown in FIG. 1C, when the outermost plating film 4 is further applied to the surface of the noble metal plating film 3, there is a problem that the adhesion between the noble metal plating film 3 and the outermost plating film 4 is lowered. .

  For this reason, the initial plating film 3a is formed by plating at a high current density for the first short time, and then the remaining plating film 3b is formed by lowering the current density. Thereby, the amount of brightener deposited on the surface of the noble metal plating film 3 can be reduced, and the contact performance and adhesion can be effectively improved.

  Here, the material, current density, and plating time when the noble metal plating film 3 is formed by plating are illustrated. All of the following plating solutions are plating solutions of Nihon Kasei Co., Ltd.

(1) Using a pure palladium plating solution having a trade name of T-10 as the plating solution, the initial plating film 3a is formed by plating at a current density of 1.0 A / dm ² for the first 1 to 10 seconds. The remaining plating film 3b is formed by plating at 0.5 A / dm ² .
(2) The initial plating film 3a is formed by plating using a palladium cobalt plating solution having a trade name of PCP-1 as the plating solution, with the current density set to 3.0 A / dm ² for the first 1 to 10 seconds, and then the current density. The remaining plating film 3b is formed by plating at 1.0 A / dm ² .
(3) Using the pure rhodium plating solution of trade name TP-2 as the plating solution, the initial plating film 3a is formed by plating at a current density of 10.0 A / dm ² for the first 1 to 5 seconds, and then the current density The remaining plating film 3b is formed by plating at 3.0 A / dm ² .
(4) A pure ruthenium plating solution having a trade name of Ru-6 is used as the plating solution, and the initial plating film 3a is formed by plating at a current density of 6.0 A / dm ² for the first 1 to 10 seconds. the remaining plated film 3b is plated as a density 2.0A / dm ^2.

  In any of the above, the pinhole 2a formed in the base plating film 2 can be appropriately sealed with the noble metal plating film 3, and the contact performance and adhesion can be improved.

  As shown in FIG. 1 (c), the pinhole 2a is preferably completely filled with the noble metal plating film 3, but the pinhole 2a is not completely filled with the noble metal plating film 3, but has a slight gap. Even if there is, a form in which the pinhole 2a is closed (sealed) with the noble metal plating film 3 is one of the embodiments.

  In FIG. 1C, the outermost plating film 4 is further formed on the surface of the noble metal plating film 3. In such a case, after the noble metal plating film 3 made of a platinum group or a platinum group alloy is formed by plating, The outermost plating film 4 can be formed by plating with Au or Ag.

  Here, examples of the platinum group alloy include Pd—Co, Pd—P, and Pd—Ni. Further, by using such a platinum group alloy, there is an effect that the crystal grains of the initial plating film 3a can be further refined.

  In this embodiment, since the surface of the noble metal plating film 3 made of platinum group or platinum group alloy can be used as the contact surface, it is not necessary to apply Au plating or Ag plating to the outermost surface, or FIG. ), The outermost plating film 4 made of Au or Ag can be formed thinner than in the prior art.

  As described above, in the present embodiment, even if the base plating film 2 made of Ni or Ni alloy is thinly formed by electrolytic plating and the pinhole 2a is formed, the pinhole 2a is formed as a fine noble metal plating film 3. It can be sealed with crystal grains, and an electrical contact excellent in corrosion resistance, post-processability, contact performance, and solderability can be manufactured along with thinning.

  In this embodiment, when the noble metal plating film 3 is formed by electroplating, for example, the current density may be set to gradually decrease from the beginning to the end of the plating, or stepwise three or more times. In addition, the current density can be changed.

  The method for changing the current density is not particularly limited. For example, there are the following methods for continuously changing the current density.

  First, as shown in FIG. 2, a base material substrate (hoop material) 35 having a formation surface for electrolytic plating of electrical contacts is prepared. A resist layer 36 is applied to the surface of the base material substrate 35, and a punching pattern is formed on the resist layer 36 in each electrical contact formation region 36 a. The hatched portion shown in FIG. 2 is the region of the resist layer 36 that remains. In FIG. 2, a large number of electrical contact formation regions 36a are arranged.

  And as shown in FIG. 3, the said base material board | substrate is arrange | positioned in the plating tank 51. FIG. The base material substrate 35 is supported so as to be movable in the direction of the arrow in FIG.

  As shown in FIG. 3, the anodes 53, 53 arranged in the plating tank 51 are on the fixed side, and the anodes 53, 53 are arranged to be inclined with respect to the moving direction of the base material substrate 35.

  In the embodiment of FIG. 3, the plating bath 51 is put into the plating bath from the left inlet and discharged from the right outlet.

  A rectifier (not shown) is connected to the anode 53 to control the current. As shown in FIG. 3, when the base material substrate 35 is moved in the direction of the arrow by disposing the anode 53, the distance between each formation region 36a provided on the base material substrate 35 and the anode 53 gradually increases. The current density acting on each formation region 36a can be reduced substantially linearly with the movement of the base material substrate 35.

  In FIG. 3, two anodes 53, 53 are provided, and a base material substrate 35 serving as a cathode is interposed between the anodes 53, 53. With this, electrical contacts are plated on both surfaces of the base material substrate 35. Can be formed. Of course, it is also possible to have only one anode 53 and to form an electrical contact on only one surface of the base substrate 35 by plating.

Further, for example, the following method can be used to change the current density in multiple stages.
As shown in FIG. 4, a mask plate 54 having a plurality of openings 55 is disposed between a base material substrate 35 that is a cathode and an anode 53. The anode 53 is arranged in parallel with the base material substrate 35. For example, as shown in the plan view of FIG. 5, the mask plate 54 is provided with a plurality of apertures 55 having different aperture diameters along the moving direction of the base material substrate 35.

  For example, as shown in FIG. 5, a mask plate 54 formed so that the aperture diameter of each aperture 55 decreases sequentially from the entrance side to the exit side in the movement direction of the base material substrate 35 is used. When the material substrate 35 is moved in the direction of the arrow in FIG. 4, the current density with respect to each formation region 36 a of the electrical contacts formed on the surface of the base material substrate 35 can be reduced stepwise as the base material substrate 35 moves.

  In the embodiment shown in FIG. 6, the anode 53 is divided into divided anodes 53 a to 53 f that are divided into a plurality along the moving direction of the base material substrate 35. The divided anodes 53a to 53f are connected to rectifiers 56a to 56f, respectively, to control the current, and the current density can be individually adjusted in each of the divided anodes 53a to 53f.

  As shown in FIG. 6, when the base substrate 35 on the cathode side is moved in the direction of the arrow, the divided anodes 53a to 53f facing the contact electrode formation regions 36a change one after another. For this reason, as the base material substrate 35 moves, the current density acting on each formation region 36a can be changed in multiple stages.

DESCRIPTION OF SYMBOLS 1 Base metal 2 Base plating film 2a Pinhole 3 Noble metal plating film 3a Initial plating film 3b Remaining plating film 4 Outermost surface plating film 35 Base material board | substrate 51 Plating tank 53 Anode 53a-53b Divided anode 54 Mask board 55 Opening 56a ~ 56f Rectifier

Claims (2)

The manufacturing method of the electrical contact characterized by having the following processes.
(A) a step of plating a base plating film of Ni or Ni alloy by electrolytic plating on a base metal;
(B) A noble metal plating film made of a platinum group or a platinum group alloy is formed by electroplating on the surface of the base plating film. At this time, the current density is increased and the initial plating is performed. The process of lowering and plating the rest. After plating the noble metal plating film consisting of a platinum group or platinum group alloys, the surface of the precious metal plating film, the manufacturing method of the electrical contacts according to claim 1, wherein applying Au plating or Ag plating.

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