JPS58117889A - Electroplating method - Google Patents

Abstract

PURPOSE:To prevent replacement plating that arises in an initial period and to obtain a plating layer of good adhesion by bringing a plating base material into contact with a plating soln. while keeping said material applied with positive micro voltage before contacting with the plating soln. then applying plating current. CONSTITUTION:Micro voltage is applied to a base material vulnerable to generation of replacement plating in the initial stage of plating prior to contacting with the plating soln. This micro voltage is the positive voltage in the range where the base material does not elute even if said material contacts with the plating soln. The voltage necessary for obtaining the good adhesion is the voltage (reverse from the voltage in the stage of plating) which is lower than the equil. voltage in the range wherein no electric current flows even if the material contacts with the plating soln. and the base material does not dissolve and which makes the base material positive. While the base material is held applied with such voltage, the material is brought into contact with the plating soln. and the plating current is applied thereon. As a result, the base material is electroplated while the clean and active surface after the pretreatment is maintained and the plating having good adhesion between the plating layer and the base material is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for completely preventing Vt displacement and obtaining a plating layer with good adhesion.

In the electroplating method, it is a well-known fact that one of the causes of significantly lowering the adhesion between the plating layer and the plating base 41 (hereinafter referred to as the base material) is the presence of t-transfer plating. The existence of this displacement plating means that even if the adhesion between the plating layer and the base material is sometimes insufficient immediately after plating, if there is a heating process in the atmosphere during the practical process after plating, the adhesion may deteriorate. It may appear conspicuously.

For example, in the case of silver plating on an iron-nickel alloy substrate, there is almost no mutual diffusion between the plating layer and the substrate even during heating, and if displacement plating is present, the resulting Due to the heating mentioned above, blistering and peeling occur between the plating layer and the base material, making it impossible to obtain good adhesion.

As a method to prevent such a decrease in adhesion, for example, a conventional method used in continuous plating is to apply a predetermined current in advance to the base material before it comes into contact with the plating bath.
After that, either put it in a plating bath or pour a plating bath to prevent displacement plating, or form a non-electrodepositable film such as a chelate film on the surface of the first substrate before starting the plating process. A so-called bre-dip method is used in which the chelate film is broken using a plating bath or electric energy and then plated.

However, in the case of the former method, especially in the case of intermittent plating using a jet flow, air entrainment,
There are variations in bath temperature, and there is also a lag in the timing of collision between the substrate and the plating solution within the plating area, resulting in uneven current density distribution in the early stage of plating, etc.
It has the disadvantage that it is not necessarily a preferable plating method in terms of quality.

In the latter case, the chelate film formed by the bleed dip may be mixed into the plating bath, causing a decrease in the purity of the plating quality, and may also be the cause of a decrease in adhesion due to the influence of impurities. Furthermore, there is a disadvantage that there are many control points during manufacturing, which reduces workability.

The present invention was made to solve the above-mentioned problems, and effectively prevents displacement plating in the initial stage of electroplating using a simple method, without reducing work efficiency, and without contaminating the plating bath. Therefore, it is an object of the present invention to provide an electroplating method capable of obtaining plating with good adhesion.

The present invention performs initial displacement plating by applying a plating current to the plating substrate after contacting the plating substrate with a positive microvoltage applied to the plating substrate before contacting the plating solution. This is an electroplating method characterized by preventing.

Electroplating to which the method of the present invention is applied is for combinations of plating substrate, plating metal, and plating bath that may cause displacement plating in the early stages of plating.

In the present invention, the microvoltage applied to the base material before contact with the plating solution is a positive voltage within a range that does not cause elution even when the base material comes into contact with the plating solution. The voltage required to obtain good adhesion is a voltage with the substrate as positive (compared to the voltage during plating), which is below the equilibrium voltage within the range where no current flows even when the plating solution comes into contact with it, and where the substrate does not elute. (opposite), and if it is too low, displacement plating may occur and the adhesion may be impaired.

With this kind of voltage applied, the VCl plating solution is started to flow or immersed in the plating solution to bring the substrate into contact with the plating solution, and then the initial air entrainment and variations in bath temperature are eliminated and the substrate is stabilized. When the liquid state is reached, a plating current is applied. In this way, the substrate is electroplated while maintaining its clean and active surface after pretreatment, so that a plating with good adhesion between the plating layer and the substrate can be obtained.

Example 4 Thickness 025101°W containing 2% by weight of nickel
A 25 zm hoop-shaped iron-nickel alloy strip was continuously degreased and pickled with an aqueous hydrochloric acid solution to clean the surface, and then silver plated using a continuous electroplating device.

A plating solution under the following conditions was used.

Before contacting the strike plating solution, a voltage of 0.05 V with the substrate as positive, which is below the equilibrium voltage, is applied to the substrate while the solution is passed through the solution, and as shown in the figure, after 2 seconds of passing the solution, the cathode current density is 5A/
After strike plating was performed for 5 seconds with d♂, the present plating bath was further used to compare the cathode current density, and the voltage from before contact with the above strike plating solution was 0. (j5 Without applying V, a plating current with the same history as described above was applied to obtain a 2.5 μm thick silver plating layer as a comparative example.

The resulting 2 m long silver-plated strip was heated in the air at 500° C. for 5 minutes, thermocompression bonded with a gold wire having a diameter of 30 μm, and then subjected to a tensile test.

As a result, no abnormality was observed in the product according to the present invention. On the other hand, in the comparative example, cracks were observed at the interface between the iron-nickel alloy surface and the silver plating layer.

From the examples, it was found that a silver plating layer with good adhesion can be easily obtained on an iron-nickel alloy by the method of the present invention, and that it is particularly effective in reducing the thickness of the plating layer.

Although the above embodiments have been described in the case of continuous electroplating, the method of the present invention can be similarly applied to the case of batch-type electroplating, and is not limited to silver electroplating on iron, nickel, and gold. This method can be applied to all combinations of metals that may cause initial displacement plating during plating. 1 - As described above, the electroplating method of the present invention involves applying a microvoltage that is positive to the plating substrate before contacting the plating solution, and then after bringing the plating substrate into contact with the plating solution. Because a plating current is applied, the base material will not elute even if the base material is brought into contact with the plating solution while a microvoltage is applied.
A clean and active surface is maintained, and plating is started when the initial air entrainment, bath temperature variations, etc. are eliminated and a stable liquid state is reached, thus preventing initial displacement plating and ensuring good adhesion. It is possible to obtain a smooth plating and to obtain a plating of a uniform quality without unevenness.As only the application of the voltage is required, there is an advantage that the equipment is simple and the 11th step is simple.

[Brief explanation of the drawing]

The figure is a diagram showing an example of the application history of plating current in an embodiment of the method of the present invention.

Claims (2)

[Claims] (1) Initial displacement plating is performed by applying a plating current to the plating base material after contacting the plating base material with a positive microvoltage applied to the plating base material before contact with the plating solution. An electroplating method characterized by preventing. (2) The electroplating method according to claim 1, wherein the microvoltage is equal to or lower than the equilibrium voltage.