JPH03215697A - Method for sealing metallic material - Google Patents

Abstract

PURPOSE:To produce a sealed metallic material having high corrosion resistance by electrolyzing the metal-plated metallic material by using an org. compd. having an SH group. CONSTITUTION:A copper alloy element, for example, is plated with Ni as the base plating and then plated with gold as the finish plating to form a connector for the electronic circuit, etc. An electrolyte consisting of about 1-4g/l of an org. compd. having an SH group (e.g. 1-phenyl-5-mercaptotetrazole), about 10-20% methanol and about 80-90% of an aq. NaOH soln. (at <= about pH9) is used to seal the pinholes generated at this time, and electrolysis is carried out at about 2-3mA/dm<2> and with the electrolyzing time of about 2-3min and electrolyte temp. of about 20-30 deg.C. Consequently, a sealed connector for the electronic circuit having high corrosion resistance or the like is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method for sealing metal materials, and more particularly to a method for sealing metal materials plated with metal.

B.. Summary of the Invention The present invention is a method for sealing a metal material, and in particular, a sealing product having high corrosion resistance is obtained by electrolytically treating a metal material plated with an SH group using an organic compound having an SH group. It is possible to obtain

C. Prior Art Conventionally, the surface treatment of connectors used for electrical connection of electronic components involves plating a copper alloy, which is the base material of the connector, with Ni plating of several micrometers as an underplating. Gold plating as finishing plating 0,
1 to 0.5 μm, respectively. Here, gold plating is applied as the final plating because gold, which has low contact resistance, is often used in connectors for electronic circuits to allow a weak current to flow therethrough.

However, due to the high cost of gold, it is necessary to reduce the thickness of the plating, which causes many pinholes to form in the gold plating layer, through which water enters and corrodes the copper alloy that is the base of the connector.

To counter this problem, a method has been devised in which a film is formed on the gold plating layer to seal the pinhole.

This method is called a sealing treatment, and is generally divided into a method of forming an organic film typified by an organic amine such as 'n-octadecylamine (ODA), and a method of forming a chromic acid film.

D. Problems to be Solved by the Invention However, all of the coatings obtained by these treatment methods have the drawback of having a small corrosion-preventing effect.

For example, in water treatment plants, large amounts of H and S exist, so this H
tS passes through the gold-plated pin pole and reacts with the copper alloy that is the connector element, producing copper sulfide.

As a result, the copper alloy that is the connector element turns black and corrodes in about one year, making it difficult to use it as an electronic circuit connector for a long time.

The present invention was devised by focusing on these problems, and it is possible to produce a metal with high corrosion resistance by electrolytically treating a metal plated metal material using a filter organic compound having an SH group. The purpose of the present invention is to provide a method for sealing a material.

E. Means for Solving the Problems As a result of intensive research to solve the above problems, the present inventor discovered that a metal material with excellent properties can be obtained by electrolytically treating an organic compound having an SH group. , completed the invention.

That is, the method for sealing a metal material according to the present invention is to electrolytically treat a metal material plated with an SH group using an organic compound having an SH group.

The present invention will be explained in more detail below.

First, the metal plated metal material used in the present invention is one that has been finished by closely covering the surface of the metal with a thin metal film by a method such as electroplating or hot-dip plating. Specifically, connectors for electronic circuits are produced by surface-treating a copper alloy element with Ni plating as a base plating and gold plating as a final plating.

However, when the gold plating layer is thin as a final plating, there are many pinholes in that layer, which corrodes the copper alloy that is the element. Therefore, in the method according to the present invention, in order to seal this pinhole, the following sealing treatment is performed.

That is, in the method according to the present invention, an organic compound having an SH group is used as a sealing agent. Examples of this compound include so-called merkabutane, which is a compound in which the hydrogen atom of an aliphatic hydrocarbon is replaced with an SH group, or a compound in which the hydrogen atom of an aromatic hydrocarbon is replaced with an SH group.
Examples include so-called thiophenol, which is a compound substituted with an H group. Specifically, mercaptoacetic acid, mercaptosic mexane, etc. as mercaptan, and thiophenol! -Phenyl-5-mercaptotetrazole, mercabutonaphthol. Examples include mercaptodiphenylmethane, and preferably 1-phenyl-5-mercaptotetrazole (hereinafter referred to as PMTA).
) can be used. This PMT A is generally known as a discoloration inhibitor for silver, but in the method according to the present invention, PMT A is dissolved by the following method and used for sealing treatment by electrolytic treatment. .

(+) Method for dissolving PMT,A First, PMTA is dissolved in an organic solvent such as methanol,
Next, an aqueous alkaline solution such as NaOH or KOH is added to form an electrolytic solution.

This is because PMTA is only soluble in organic solvents, and electrolytic treatment cannot be performed unless it is made water-soluble. For this purpose, PMTA is first dissolved in an organic solvent, and then an aqueous alkaline solution is added to form an electrolyte. The PMTA electrolyte composition obtained in this way has a PMTA of 1 to 4 g/I.
2. Preferably 1.5g/L methanol is lO~20%
, preferably 20%, NaOH aqueous solution 80-90%,
Preferably it is 80%. Here, add 1 to 4 g of PMTA/
The reason for setting 2 is that if it is less than lg/I2, the contact resistance will be large and it cannot be used in electronic parts, for example, to pass a weak current.If it exceeds 4g/ff, PMTA will be difficult to dissolve in organic solvents such as methanol. To become.

Moreover, the reason why methanol is set to 10 to 20% is because PMTA becomes difficult to dissolve when it is less than 10%, and because when it exceeds 20%, the current density of the electrolytic solution is significantly reduced.

Note that the pH of the NaOH aqueous solution is 9 or more, preferably in the range of 9 to IO.

This is because the current density of the electrolytic solution decreases significantly when the pH is less than 9, and because PMTA becomes difficult to dissolve in an acidic region.

Incidentally, the electrolytic treatment method according to the present invention is thought to involve the following reaction, although it is not intended to be particular about the theory.

In other words, since organic compounds with SH groups exist as SH" ions in the electrolyte, the contact is connected to the positive electrode (÷ electrode).
By using stainless steel as the cathode (single pole) and electrolyzing it, an organic compound forms a film on the pinholes on the surface of the metal material.

This film formation is considered to be chelate formation between the metal material and the organic compound.

Chelate form (2) electrolytic treatment conditions resulting from the reaction of PMTA and Cu: A metal material plated with metal is immersed in the electrolytic solution obtained by the PMTA dissolution method described in (1) above, and the following conditions are applied. Electrolytic treatment is performed to form a sealing film.

That is, the electrolytic conditions are a current density of 2 to 3 mA/d.
m "preferably 3 m A/d m", electrolysis time 2 to 3 minutes, solubility at room temperature, preferably 20 to 30 °C
It is.

The reason why the current density is set to 2 to 3 mA/dm'' is because of the relationship with the methanol concentration mentioned above, and because a higher current density cannot be obtained. However, a higher current density is preferable. Therefore, it is preferable to use 3 mA/dm'.The reason why the melting temperature is set to room temperature is that if the temperature is too high, methanol will evaporate and PMTA will be difficult to dissolve.

The sealed metal material obtained by the electrolytic treatment according to the present invention has high corrosion resistance and can be suitably used for electrical parts and the like.

F. Examples Hereinafter, a detailed explanation of the method for sealing a metal material according to the present invention will be explained based on examples.

Example 1 Relationship between methanol density and PMT A dissolution When an aqueous NAOH solution (pH 9.0) was added to methanol, the methanol δ degree was 0.1θ%. 20%. 30%.
Adjust the methanol concentration and PMTA to 40%.
The relationship between solubility was investigated. The results are shown in FIG. 1st
As shown in the figure, it can be seen that the higher the methanol concentration, the higher the PMTA solubility.

Example 2 An example of the relationship between methanol concentration and current concentration! From the results obtained, an aqueous NAOH solution (pH 9.0) was added to methanol so that the final concentration of PMTA was 2 g/12
) to make the methanol concentration O. 10%, 20
%, 30%, 40%. The methanol concentration and electrolytic current density were examined.

The results are shown in FIG. As shown in FIG. 2, it can be seen that when the methanol concentration exceeds 20%, the current density decreases significantly. Example for this! As shown in FIG. 1, when the methanol concentration is less than 20%, the PMT A solubility decreases significantly. Therefore, it can be seen that a methanol concentration of 20% is optimal as a harmonious point that satisfies both the conditions of obtaining a higher current density and obtaining a higher PMTA solubility.

In addition, from Figure 1, at a methanol concentration of 20%, PMT
It can be seen that the solubility of A is approximately 2 g/Q. However, in the method according to the present invention, it is necessary to sufficiently dissolve PMTA, so the PMTA concentration! ．． It was determined that 5 g/i2 was optimal.

Example 3 Relationship between electrolyte pH and current density From the results obtained in Example 2, the final concentration of PMT A was 1.5 g/
12 and N such that the final concentration of methanol is 20%.
When aOH aqueous solution was added, the pH was 6.7, 8, and 6.7, respectively.
Adjust the electrolyte so that it becomes 9, 10.11 and 12,
The relationship between the pH of the electrolyte and current density was investigated.

The results are shown in FIG. As shown in Figure 3, the pH is 9.
It can be seen that the highest current density can be obtained in the above manner. In the method according to the present invention, the optimum pH was determined to be in the range of 9 to IO, taking into account the ease of adjusting the pH range.

Example 4 Relationship between PMTA concentration and contact resistance Ni was used as the base plating to a thickness of 2 μm, and gold was used as the final plating to a thickness of 0.0 μm.
Phosphor bronze plated to 2μm in methanol
Dissolve MTA, final concentration 0.5 g/l2, I
g/12.2g/ρ. 3 g/(1.4 g/(!tL, methanol concentration 20% obtained in Examples 1 to 3, N
An AOH aqueous solution (pH 9.0) was prepared and immersed in f-2 electrolyte.

Next, electrolytic treatment was performed at 25°C for 2 minutes at a current density of K 3 mA/dm', and the resulting pore-sealed phosphor bronze was treated with an SOZIA degree of 10 ppm at 40°C. Relative humidity 80%
A corrosion resistance test was conducted and the contact resistance was measured.

The results are shown in FIG. PMTA as shown in Figure I
Concentration is 1-4g, Q! You can see that the contact resistance is low.

In addition, from the relationship between f2 PMT A solubility, methanol concentration, and current density shown in Example 2, PMTAm degree is 1.5.
/& was optimal.

Example 5 SO, exposure test and contact resistance Regarding the sealed phosphor bronze according to the present invention obtained in Example 4, a conventional sealed product (Rikiichi Dodge Connector. Manufacturer: KEL) ) and an untreated product were used as comparison sides, and the relationship between the SO2 exposure test and the contact resistance was investigated in the same manner as in Example 4.

The results are shown in FIG. As shown in Fig. 5, the phosphor bronze sealed by the method of the present invention is 1.5 to 2 times and 1.
It can be seen that the corrosion resistance is 0 to 20 times higher.

G. Effects of the Invention According to the present invention, a sealed product having high corrosion resistance can be obtained by electrolytically treating a metal plated metal material using an organic compound having an SH group, particularly PMTA.

Therefore, the pore-sealing product produced by the method of the present invention has a great corrosion prevention effect, and therefore does not generate sulfides even in water treatment plants where large amounts of H and S are present.

Therefore, even when the pore-sealed product according to the method of the present invention is used in, for example, an electronic circuit connector, corrosion due to blackening does not occur, and therefore it can be used for a long time.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between methanol concentration and PMTA dissolution change, Figure 2 is a graph showing the relationship between methanol concentration and current density change, and Figure 3 is a graph showing the relationship between electrolyte pH and current density change. FIG. 4 is a graph showing the relationship between P M TAa degree and contact resistance, and FIG. 5 is a graph showing the relationship between S O 2 exposure test and contact resistance. Figure 1 Relationship between methanol concentration and PMTA solubility Methanol (%
) / Alkaline aqueous solution Figure 2 Relationship between methanol concentration and current density Methanol (%) / Alkaline aqueous solution Figure 3 Relationship between pH of electrolyte and current density 0 1 2 3 4 5 6 F8 9 10 11 12 (ρH) Electrolysis pH of solution Figure 4 Relationship between PMTA concentration and contact resistance O 1 2 3 4 (9/breath) P~ITAjl degree Figure 5 S O t Relationship between exposure test and contact resistance SOI exposure test

Claims (2)

[Claims] (1) A method for sealing a metal material, which comprises electrolytically treating a metal plated metal material using an organic compound having an SH group. (2) The organic compound having an SH group is 1-phenyl-5-
The method for sealing a metal material according to claim (1), wherein mercaptotetrazole is used.