JPH05339741A - Substitution tin plating method for copper material - Google Patents

Abstract

PURPOSE:To always form a uniform Sn-plating film without defects for substitution Sn plating on Cu parts by controlling the concn. ratio of Sn ion to Cu ion in the plating liquid to a specified value. CONSTITUTION:In the process of substitution Sn plating on Cu parts, Cu parts are dipped in a substitution Sn plating liquid containing dissolved tin (II) chloride, sodium cyanate, and sodium hydroxide. While plating proceeds, the concn. of Sn ion in the plating liquid decreases and the concn. of Cu ion increases by dissolution of Cu from the Cu parts, and this causes defects in plating. Therefore, concns. of Cu ion and Sn ion are always measured and controlled to keep the ratio of Cu ion conc./Sn ion concn. to <=0.7. By this method, production of defective plating film is prevented and the obtd. Sn plating film is always uniform. Moreover, excess discharge or excess supply of Sn ion can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substitution tin plating method for copper materials, and more specifically, substitution tin plating for copper plates used as electronic substrates, water / hot water supply pipes, copper tubes used as heat exchanger tubes for heat exchangers, etc. It relates to a method of applying a treatment.

[0002]

2. Description of the Related Art Conventionally, tin plating is applied to the inner surface of a copper plate for an electronic substrate, a copper pipe for piping, or a copper pipe for heat transfer tubes to improve corrosion resistance and prevent elution of copper ions. .. In the tin plating process of such a copper material,
The plating bath once constructed is used continuously while replenishing the main bath components, but the experience of bath management is largely dependent on the fact that when a certain area is plated, a predetermined amount of the main bath is used as a guide for the treated area. Ingredients are often replenished. In addition, the concentration of tin ions in the bath is measured and the shortage is replenished on the basis of the time of building the bath. However, these bath management methods have problems such as a decrease in plating thickness and an increase in plating unevenness as the treated area increases.

[0003]

As a result of repeated studies on the relationship between the occurrence of defects in tin plating and the composition of the plating bath, the inventors have found that when a plating defect occurs, a large amount of copper ions are present in the plating bath. It was discovered that the tin ion concentration and the copper ion concentration were close to each other in the plating bath where the plating failure was likely to occur, and as a result of further investigation, the substitution tin plating showed that the substitution reaction of tin ion and copper ion However, the potential difference between the two ions in the bath, which is the driving force for the substitution reaction, is brought about by the difference in the activity of both ions in the bath. We have found that relative management is needed.

The present invention was developed based on the results of the above research, and its purpose is to always obtain a uniform plating film without defects and prevent the discharge of excessive plating solution and the replenishment of excessive chemical solution. (EN) It is possible to provide a tin plating treatment method for a copper material, which is capable of bath management.

[0005]

The tin plating treatment method for a copper material according to the present invention for achieving the above object is a method of performing displacement tin plating on a copper material, wherein the plating bath is controlled by tin ions in the bath. It is carried out based on the concentration ratio with copper ions, preferably by controlling the ratio of the tin ion concentration to the copper ion concentration in the plating bath and the copper ion concentration / tin ion concentration within the range of 0.7 or less Characterized by obtaining a plating film.

Substitution tin plating proceeds by a substitution reaction between tin ions and copper ions, and the potential difference between the two ions in the bath, which is the driving force for the substitution reaction, is most affected by the activity or concentration of each. Therefore, in order to obtain a uniform plating film having no defects in the copper material plating treatment step, bath management may be performed based on the concentration ratio of tin ions and copper ions.
Preferably, the ratio of the tin ion concentration to the copper ion concentration in the plating bath and the copper ion concentration / tin ion concentration are controlled within the range of 0.7 or less. When the ratio of copper ion concentration / tin ion concentration in the bath exceeds 0.7, the substitution reaction rate decreases, uneven plating is likely to occur, and the deposition rate becomes slow. In addition, although a complex forming agent that forms a complex with copper ions may be added to the displacement plating solution, many experiments have confirmed that the concentration does not practically affect the tin plating reaction.

[0007]

In the present invention, the potential difference between the two ions in the bath, which is the driving force for the tin ion-copper ion substitution reaction that promotes tin plating, is always correct by keeping the concentration ratio of both ions within a predetermined range. Since it is adjusted, the deposition rate of the plating film becomes constant, and a uniform and effective plating film is formed.

[0008]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Example 1 A displacement plating solution containing stannous chloride 18.8 g / l, sodium cyanide 188 g / l, and sodium hydroxide 22.5 g / l (tin concentration 9.9
g / l) and changing the copper ion concentration / tin ion concentration ratio to obtain phosphorous deoxidized copper plate (JIS H3100 C1220, dimensions: 0.5 mm thickness x
(50 mm width × 100 mm length) was used as the object to be plated, the surface was activated with a mixed solution of sulfuric acid and nitric acid, and then substitutional tin plating was performed.
The ratio of copper ion concentration / tin ion concentration in the plating bath was changed by adding copper sulfate, and the plating treatment was carried out under the conditions of a plating bath temperature of 333 K, a liquid volume of 2 l, and an immersion time of 10 minutes. After the plating treatment, the presence or absence of plating unevenness was visually observed, and the film thickness was calculated by melting the plating film and measuring the mass difference. Further, the plated copper plate was immersed in tap water for 24 hours to measure the amount of copper ion elution. Table 1 shows the relationship between the copper ion concentration / tin ion concentration ratio in the plating bath and the plating film evaluation results and film thickness measurement results. From Table 1, it was confirmed that when the ratio of copper ion concentration / tin ion concentration was 0.7 or less, the plating thickness was constant, there was no plating unevenness, and the elution of copper ions was small.

Comparative Example 1 Using the same substitution tin plating solution as in Example 1, a phosphorous deoxidized copper plate having the same material and size as in Example 1 was used as the object to be plated, and the ratio of copper ion concentration / tin ion concentration in the plating bath was To 0.8 and 1.2
Substitution tin plating was performed under the same conditions as in Example 1, and after the plating treatment, the same plating film evaluation and film thickness measurement as in Example 1 were performed. The results are shown in Table 2. As seen in Table 2, when the copper ion concentration / tin ion concentration ratio in the plating bath exceeds 0.7, plating unevenness occurred and the film thickness varied.

[0010]

[Table 1]

Example 2 A phosphorus-deoxidized copper tube was used using a displacement plating solution (tin concentration: 3.2 g / l) consisting of stannous chloride 6 g / l, thiourea 55 g / l and tartaric acid 39 g / l.
(JIS H3300 C1220, dimensions: outside diameter 22.22mm × thickness 0.81mm ×
The surface of the copper tube was activated with a mixed solution of sulfuric acid and nitric acid, and the inner surface of the copper tube was subjected to substitution tin plating. The copper ion concentration / tin ion concentration ratio in the plating bath was changed by adding copper sulfate, and the plating treatment was carried out under the conditions of a plating bath temperature of 333 K, a liquid volume of 20 l, and a circulating water passage time of 10 minutes. After the tin plating treatment, the film thickness was calculated by visually observing the occurrence of unevenness in the plating film and melting the film and measuring the mass difference. Further, tap water was filled in the plated copper pipe for 24 hours, and the amount of eluted copper ions was measured. Furthermore, in order to examine the pitting corrosion resistance, temperature ^{_{60 ℃, pH7, SO 4 2}} - / HCO 3 - = 1.67, Cl - 10ppm, R-
It was immersed in water containing Cl 0.5 to 2.0 ppm for 40 days. Table 2 shows the plating film evaluation results and the film thickness measurement results. As shown in Table 2, when the copper ion concentration / tin ion concentration ratio in the plating bath was 0.7 or less, there was no plating unevenness, the film thickness was constant, and pitting corrosion resistance was excellent.

Comparative Example 2 Using the same substitution tin plating solution as in Example 2, and using a phosphorous deoxidized copper tube of the same material and size as in Example 2 as a plated body, the ratio of copper ion concentration / tin ion concentration in the plating bath was set. To 0.9 and 1.1
Substitution tin plating treatment was carried out under the same conditions as in Example 2, and the copper film after the plating treatment was subjected to the same plating film evaluation and film thickness measurement as in Example 2. As shown in Table 2, the results show uneven plating, large variation in film thickness,
The pitting corrosion resistance was also poor.

[0013]

[Table 2] [Table Note] 1. Appearance evaluation ○: With plating unevenness ×: Without plating unevenness 2. Pitting corrosion resistance (maximum corrosion depth) ◎: 30 μm or less ○: 30
〜50μm △: 50〜100μm ×: 100μm or more

[0014]

As described above, according to the present invention, an effective plating film having no defects can always be obtained, and it is possible to prevent the discharge of the excessive plating solution from the plating bath and the replenishment of the excessive chemical solution to the plating bath. .. Moreover, the frequency of replenishment of the chemical liquid can be reduced.

Claims (2)

[Claims] 1. A method for performing substitutional tin plating on a copper material, characterized in that a uniform plating film is formed by controlling the plating bath based on the concentration ratio of tin ions and copper ions in the bath. Substitution tin plating method of material. 2. The substitution tin plating method for a copper material according to claim 1, wherein the concentration ratio of tin ions and copper ions in the plating bath and the copper ion concentration / tin ion concentration are controlled within a range of 0.7 or less.