JPS58147581A - Gold plating method - Google Patents

Abstract

PURPOSE:To obtain a thin gold plating film having less pinholes and excellent corrosion resistance and oxidation resistance by interrupting the conduction of electricity for electroplating, applying strike plating of platinum group metals and again applying the electroplating in succession. CONSTITUTION:In a stage of forming a gold plating film on an underlying metallic material by electroplating, the period for forming the gold plating film is divided to plural times by interrupting the conduction of electricity to a plating bath one or twice, and strike plating of platinum group metals such as gold, palladium or the like is applied in said period when the conduction of electricity is interrupted. The plating bath contg. metallic ions to be plated in a concn. lower than the concn. thereof in ordinary plating baths is used for the above- mentioned strike plating, and the uniform plating is accomplished under the conditions of large current density, a short time and low current efficiency, whereby the pinholes of the gold plating film are decreased considerably and corrosion resistance, oxydation resistance, etc. are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming a relatively thin gold-plated refill applied to electrical contact portions of electrical components such as beam connectors and switches.

[Technology background]

The gold-plated film commonly used for electrical contacts in electrical components such as relays, connectors, and switches is copper or DLV.
It protects the surface of the contact base metal material made of real copper from corrosion and oxidation caused by gases contained in the environmental atmosphere in which these electrical parts are used, and maintains the storm-like 'galvanic' contact at the point m for a long period of time. On the other hand, it is desirable from an economic point of view that the film thickness be as thin as possible.However, in practice, there is a range in which the film thickness can be made thinner (KFi), so it is necessary to make it 4 thinner than this limit. Therefore, the diameter and number of pinholes present in the plating film rapidly increase, making it impossible to obtain sufficient corrosion resistance and oxidation resistance.

Usually, gold plating exclusively formed for the above purpose is l*
m11! If the electrical part is used in a corrosive atmosphere, it will be deposited to a thickness of 9 degrees.

In particular, when used in applications that require a high degree of reliability, it may be applied to a thickness of about Lli or Itm. From the above situation, regarding the method of forming the gold plate, The main challenge for improvement is to find a method in which the number of pinholes present in the resulting plated film is as small as possible at the same film thickness.

[Conventional technology and problems]

Conventionally, an electroplating machine has been used to form a relatively thin gold plating film of about s'#m, and in that case, electricity is applied to the plating bath for a certain period of time until a predetermined film thickness is reached. Normally, it is carried out continuously.90On the other hand, the present inventor has recently proposed a method for quick gold plating that is even more corrosion resistant, by interrupting the supply of electricity to the plating bath once or twice or more, and then A method has been proposed in which the time for forming a thick gold plating film is divided into multiple periods. It was confirmed that the gold-plated film obtained by this method had significantly fewer pinholes in the corrosion resistance test than the gold-plated film obtained by the above-mentioned continuous energization and had a thickness of 94 mm. [Object of the Invention] The present invention is as described above! The purpose of this invention is to provide an improved method that enables the formation of a gold plating film with better corrosion resistance than that proposed by the running force method.

That is, considering the method already proposed by Mayuki, when forming gold plating instead of electroplating K, electricity to the plating bath is interrupted, and the opening when a gold plating film of a predetermined thickness is formed is divided into multiple periods. (Thus, the number of pinholes present in the final gold-plated film of a predetermined thickness can be reduced substantially by interrupting the supply of electricity to the plating bath and stopping the formation of the plating film.) This is considered to be a rounding effect in which the influence of the growth history of all the crystal grains forming the plating film formed before the interruption of current supply is canceled out during this period.

The pinholes that are formed after the current supply to the bath is restarted are not necessarily located so as to overlap the pinholes that are present in the cut film that were formed before the current supply was interrupted. As a result, this misalignment has the effect of reducing the number of pinholes penetrating the entire plating layer. The number of holes decreases.◎ According to the above considerations, it is possible to reduce the number of pinholes by introducing a means to actively negate the influence of the growth history of crystal grains as described above during the interruption period of current supply to the plating bath. It is possible to further reduce it to *@.

[Structure of the invention]

Therefore, in order to achieve the above purpose, the inventor of the present invention
Strike plating treatment of platinum group metals such as palladium,
In other words, by using a plating bath with a lower concentration of cutting metal ions than a normal plating bath, and by introducing a process that achieves uniform plating 11 at a high current density and under conditions where the plating current efficiency is low. A gold-plated film with significantly better corrosion resistance than any of the conventional methods was obtained.

That is, 1 the present invention is a method for forming a gold-plated film by electroplating, in which the supply of electricity to the plating bath is interrupted once or twice or more, and during this interruption period, % of the surface of the gold-plated film that has already been formed is removed. It is characterized by performing strike plating treatment of platinum group metal.

The following is 5j of the present invention! An example will be explained.

(Actual 8111fIll) Gold plating base metal material: Phosphor bronze plate (ODSl?) Dimensions
Width Length Thickness 11, 6 smx m Omx 0.6MPH-1sO
, Temperature: 60°C PH-6.5, m&1111 After the surface of the base metal material was previously plated with nickel to a thickness of 1·15Il, it was plated with a current density of 0.5I in the same gold plating bath. After forming a gold plating with a thickness of 1A/dm"4 (0)#m, strike plating is applied to the surface, that is, plating with a lower concentration of metal ions to be plated than in a normal plating bath. Although the current efficiency of plating is lower than that of plating at a high current density using a bath, the plating process is performed in the dark for a short time so that uniform plating can be achieved.

That is, in the gold strike plating bath described above, at a TILR density of OIA/s1m, the rate of 10 seconds is approximately 0.057w.
Gold strike plating treatment was performed to a thickness of m. After that, 0.4 sm of gold plating was further formed under the conditions described above.

(Example power) In Example 1, the following palladium strike plating bath was used for the gold strike plating bath (l), and in this bath, the current density was 1 degree, 1 kOA/dos"Kk, and about 0.01 m for 5 seconds. Palladium strike plating with a thickness of 8+
0 Palladium strike plating bath (Nippon Kou V Ctroblating Engineering Airs II) PH-9,1 temperature 40C (Comparative example 1) In Example 1, a 1 μm layer was continuously applied without gold strike plating. O with a gold-plated film formed (Comparative Example 2) After forming a gold-plated film of OS μm in Example 1, the current supply to the plating bath was temporarily interrupted, and the plate was removed without gold strike plating. Continuation 1!Additionally form a 0.6 μm gold-plated film and heat the above sample (Test Example 1) with 5 on-nitrogen containing lOppm of sulfide water.
After being exposed to a corrosive atmosphere at room temperature of 80% oxygen and 90% relative humidity, it was examined using an optical microscope at a magnification of 4.
The corrosion points were counted at a magnification of 90. The results of counting the corrosion points for the four samples mentioned above are shown in Table 1. ) Example 17 Example s8 Comparative Example 1 46 Comparative Example S SO (Test Example 3) To verify the possibility of reducing the gold plating film thickness with practical corrosion resistance by the gold plating method of the present invention] For each of the previous four examples, samples with different gold plating film thicknesses were prepared under nine conditions.
The corrosion test shown in Test Example 1 was carried out to determine the number of corrosion points per li m'' of 46 samples from these samples. The composition and film thickness of the plated film were as shown in Table 3. O Table 2 Composition of the plated film Total gold plating kb'1 □l Co 〒g J? Film thickness (, pm) Gold strike Gold (On) 0.66 Example゛ Gold (0 yam) (., .6) Same parameter as ゛758 Gold (Oj) 0.66 Example 1 Gold (0,11) , A, (.0.) Comparative example 1m (14)) l
Comparative Example 8 Same as oo Gold (04) Gold (o, *) 0.
Same as 8 [Effect of the invention] Based on the number of occurrences of corrosion in the test, it is clear that the improvement can be achieved by 8 to 16 times compared to the conventional method. In addition, the thickness of one gold plated film of 1 μm or more, which is required for conventional corrosion resistance standards, is
It has been shown that the present invention can be reduced to the level of 6G, and it is clear that the present invention is effective in improving economic efficiency.

Claims (1)

[Claims] In the process of forming a gold plating layer of a predetermined thickness by electroplating, the period during which the supply of electricity to the plating bath is interrupted to form the gold plating film is divided into multiple periods, and during this period when the supply of electricity is interrupted, the platinum group metal is A gold plating method characterized by carrying out a strike plating process.