JPH0527710B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is directed to copper and copper, which are characterized by using an organic sulfonate, thiourea, iminodiacetic acid, an antioxidant, and an appropriate amount of a surfactant as common soluble salts of tin and lead. This invention relates to electroless soldering baths on alloys. [Prior art and its problems] Copper and copper alloys are widely used as suitable electrically conductive materials in parts for light electrical and electronic industries.
However, copper is easily oxidized in the air, deteriorating its solderability and, in some cases, causing wire breakage due to corrosion, so soldering is performed in advance. There are two methods of soldering on copper and copper alloys: electroplating and electroless plating. In the electroplating method, the current distribution to the object to be plated, which has a complex shape, is not uniform, and it is not possible to plate the inside of parts with bends or shielding parts. However, the electroless plating method It uses a chemical reaction, and can be plated to the inside of parts with complex shapes. Many conventional electroless plating baths contain stannous chloride.
The main component is a mixed solution of lead chloride-thiourea or stannous borofluoride-lead borofluoride-thiourea, and a reducing agent, a complexing agent, etc. are added thereto. However, in the chloride bath, a precipitate of lead chloride-thiourea complex is formed at room temperature, so when preparing the plating bath, the temperature should be adjusted to 70°C.
It has the disadvantage that it does not become a transparent liquid unless it is sufficiently stirred at a temperature above ℃. In addition, this type of electroless soldering bath has a low plating speed, and when the plating speed is increased at a high temperature, the resulting plating layer becomes coarse crystals or an uneven plating film.
It also had the disadvantage of poor adhesion. On the other hand, the borosilicate bath allows the preparation of transparent solutions even at low temperatures, and has achieved considerable results in improving the appearance compared to the chloride bath. However, the hofuting bath is corrosive and
It is highly toxic and not only puts a heavy burden on plating equipment and work, but also makes wastewater treatment extremely difficult. Although the problem of borofusate can be solved by using advanced processing technology, processing requires a large amount of money, and there is considerable economic loss. Furthermore, when electronic parts come into contact with these halides, they not only corrode but also have a negative effect on electrical properties, so a halogen-free plating bath is desired. [Means for Solving the Problems] The present invention was invented in view of the above-mentioned problems, and uses an organic sulfonic acid bath, which is less problematic in terms of environment and pollution control, in place of the chloride bath and the borosilicate bath. Therefore, without causing the above-mentioned problems,
An object of the present invention is to provide an electroless soldering bath that is halogen-free, has good appearance and adhesion, and can provide a thick plated film. The configuration of the present invention will be described below. The plating bath used in the present invention includes organic sulfonic acids selected from the group consisting of (a) and (b) below, divalent tin salts and lead salts of these organic sulfonic acids,
It contains thiourea, iminodiacetic acid, an antioxidant, and an appropriate amount of a surfactant. (a) General formula (R ₁ ) _o -R-SO ₃ H [Here, R represents a C _1-5 alkyl group, and R ₁ represents a hydroxyl group, an aryl group, an alkylaryl group, a carboxyl group, or a sulfonic acid group. and may be located at any position of the alkyl group, n
represents an integer of 0 to 3] An aliphatic organic sulfonic acid represented by: (b) General formula [Here, R ₂ represents a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, a carboxyl group, or a sulfonic acid group, and m represents an integer of 0 to 3.] An aromatic sulfonic acid represented by the following. Among the above organic sulfonic acids (a) and (b) used in the electroless plating bath of the present invention, particularly important ones are listed in the following table.

〔Example〕

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these examples. Example 1 An electroless soldering bath having the following composition was prepared. Divalent ions (added as an aqueous solution of tin 2-hydroxypropanesulfonate) 8g/ Tin ions (added as an aqueous solution of lead 2-hydroxypropanesulfonate) 12 〃 2-hydroxypropanesulfonic acid 50 〃 Thiourea 80 〃 Iminodi Acetic acid 2 Hydroquinone 0.5 g/Polyethylene glycol nonyl phenol ether 1 The obtained soaking bath was heated to 75°C, and the degreased and pickled copper plate was immersed for 20 minutes. The solder alloy composition of the obtained damping layer was 52.9% Sn and 47.1% Pb.
Its thickness was 6.1 μm. The resulting plating film had fine crystals, and the plating layer did not peel off even when bent by 180°. Example 2 An electroless soldering bath having the following composition was prepared. Divalent tin ion (aqueous solution of tin methanesulfonate)
10g/lead ion (added as an aqueous solution of lead methanesulfonate) 10 〃 Methanesulfonic acid 30 〃 Thiourea 100 〃 Iminodiacetic acid 5 〃 Pyrocatechol 1 〃 7 moles of ethylene oxide adduct of styrenated phenol 0.5 〃 Obtained weight The bath was heated to 60°C, and the degreased and pickled brass plate was immersed for 30 minutes. The solder alloy composition of the obtained damping layer was 43.8% Sn and 56.2% Pb.
Its thickness was 6.8 μm. The resulting flecked film had a good appearance as in Example 1. Comparative Example 1 An electroless soldering bath having the following composition was prepared. Stannous chloride 10g / Lead chloride 5 Thiourea 120 Sodium hypophosphite 20 EDTA 30 Gelatin 1 PH (HCl) 1.2 Heat the resulting soaking bath to 75℃, degrease and pickle. The brass plate was soaked for 15 minutes. However, a lead chloride-thiourea complex precipitated from the plating bath, and the resulting solder plating was very non-uniform and only a thin plating layer was obtained. Example 3 An electroless soldering bath having the following composition was prepared. Divalent tin ion (added as an aqueous solution of tin 2-carboxyethanesulfonate) 18g/ Lead ion (added as lead 2-carboxyethanesulfonate) 12 〃 2-carboxyethanesulfonic acid 50 〃 Thiourea 100 〃 Iminodiacetic acid 2 〃 Pyrocatechol 0.5 〃 Polyoxyethylene polyoxypropylene ether 1 〃 The obtained soaking bath was heated to 75°C, and the degreased and pickled copper plate was immersed for 20 minutes. The solder alloy composition of the obtained tinted layer was 78.6% Sn and 21.4% Pb.
Its thickness was 5.3 μm. Example 4 An electroless soldering bath having the following composition was prepared. Divalent tin ions (added as an aqueous solution of tin p-phenolsulfonate) 9 g/ Lead ions (added as an aqueous solution of lead p-phenolsulfonate) 11 〃 p-phenolsulfonic acid 20 〃 Thiourea 80 〃 Iminodiacetic acid 2 〃 Resorcinol 0.5 Polyethylene glycol nonyl phenol ether 1 The obtained soaking bath was heated to 70°C, and the degreased and pickled copper plate was immersed for 15 minutes. The solder alloy composition of the obtained damping layer was 64.7% Sn and 35.3% Pb.
Its thickness was 4.8 μm. Example 5 An electroless soldering bath having the following composition was prepared. Divalent tin ions (added as an aqueous solution of tin methanesulfonate) 8g/ Lead ions (added as an aqueous solution of lead methanesulfonate) 12 〃 2-Hydroxypropanesulfonic acid 50 〃 Thiourea 80 〃 Iminodiacetic acid 3 〃 Phloroglycinol 1 Polyoxyethylene stearyl ether 1 The obtained soaking bath was heated to 60° C., and a degreased and pickled brass pipe (φ17.5×100 mm) was immersed for 15 minutes. As a result of cutting and inspecting the pipe, it was found that both the inner and outer surfaces of the pipe were plated uniformly, and the thickness of the resulting plating layer was 4.2 μm. The composition of the plating layer is
The content was 68.4% Sn and 31.6% Pb, and the plated surface was dense and had a good appearance. Comparative Example 2 An electroless soldering bath having the following composition was prepared. Divalent tin ion (added as an aqueous solution of tin 2-hydroxypropanesulfonate) 8g/ Lead ion (added as an aqueous solution of lead 2-hydroxypropanesulfonate) 12 〃 2-hydroxypropanesulfonic acid 50 〃 Thiourea 80 〃 Hydroquinone 0.5 〃 Polyethylene glycol nonyl phenol ether 1 〃 The obtained soaking bath was heated to 75°C, and the degreased and pickled copper plate was immersed for 20 minutes. The solder alloy composition of the obtained tinted layer was 74.7% Sn and 25.3% Pb.
Its thickness was 1.64 μm. The film thickness was thinner than in Example 1, and it was confirmed that the addition of iminodiacetic acid was effective in increasing the film thickness. [Effects of the Invention] As explained above, since the present invention uses a halogen-free bath, it has the effect of significantly extending the life of electronic components and making it easier to solder them.

Claims (1)

[Scope of Claims] 1 Organic sulfonic acids selected from the group consisting of (a) and (b) below, divalent tin salts and lead salts of these organic sulfonic acids, thiourea, iminodiacetic acid, oxidation An electroless soldering bath characterized by containing an inhibitor and a surfactant. (a) General formula (R ₁ ) _o -R-SO ₃ H [Here, R represents a C _1-5 alkyl group, and R ₁ is a hydroxyl group, an aryl group, an alkylaryl group, a carboxyl group, or a sulfonic acid group. and may be located at any position of the alkyl group, and n represents an integer of 0 to 3]. (b) General formula [Here, R ₂ represents a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, a carboxyl group, or a sulfonic acid group, and m represents an integer of 0 to 3.] An aromatic sulfonic acid represented by the following.