JPS5910997B2 - Tin and tin-lead alloy plating liquid - Google Patents

Description

[Detailed description of the invention] The present invention relates to a tin or tin-lead alloy plating solution.

Traditionally, sulfuric acid baths or fluorinated baths were used as tinning baths.
Further, a borofluoride bath has been mainly used as a tin-lead alloy plating bath.

However, borofluoride is a compound that is very difficult to treat as wastewater, and a large amount of treatment equipment and treatment costs are required for the treatment of borofluoride plating bath waste liquid and washing water.

In addition, borofluoride is highly corrosive, which limits the materials used for plating equipment, making equipment maintenance difficult.Furthermore, it generates harmful gases, creating problems in the working environment, which is undesirable from the standpoint of pollution prevention and environmental hygiene. It's not a pampering bath. In addition, plating baths containing 10 main ingredients, sulfonate, pyrophosphate, and sulfamate, have been announced as plating baths that do not contain borofluoride, but they all have poor uniform electrodeposition properties and do not produce smooth, dense plating. It is difficult to obtain a film and is not satisfactory as a tin or tin-lead alloy plating bath.

In view of the above circumstances, an object of the present invention is to provide a tin and tin-lead alloy plating solution that does not cause pollution problems and has excellent electrodeposited film properties.

The present invention provides: (1) a stannous salt, or a stannous salt and a lead salt; At least one selected compound; and 011
) This relates to a tin or tin-lead 25 alloy plating solution characterized by containing a surfactant.

The present invention also relates to the tin or tin-lead alloy plating solution further containing hydrazine or a salt thereof. The metal salts used in the present invention are not particularly limited, and are those commonly used in tin and lead plating baths.

For example, as the stannous salt, stannous chloride, stannous sulfate, stannous acetate, etc. are used, and as the lead salt, lead nitrate, lead acetate, lead carbonate, etc. are used. 35 The concentration of the metal salt used in the plating bath is 1 to 409/l as metal tin, preferably 5
~20g/l is suitable, and as metal lead 0.5~40g/l
1/l, preferably 1 to 159/2, is suitable.

Further, the total metal concentration is preferably 509/l or less. this? When the concentration is above, the viscosity of the liquid increases and the amount of pumping increases, which is uneconomical. Examples of the alkali salts of gluconic acid or glucoheptonate used in the present invention include sodium gluconate, potassium gluconate, sodium glucoheptonate, potassium glucoheptonate, and the like.

Lactone refers to a compound containing an ester functional group in the ring, and is classified into β-lactone, γ-lactone, δ-lactone, etc. depending on the number of atoms constituting the ring. Compounds having a hydroxyl group and a carboxyl group in the molecule, such as gluconic acid and glucoheptonic acid, easily form an intramolecular ester by heating or the like to become a lactone. In an aqueous solution, free gluconic acid, γ-lactone, and δ-lactone do not exist alone, but exist as an equilibrium mixture of the three, with some of them changing into the other two. The composition of the equilibrium solution varies depending on the solvent, pH, temperature, concentration, etc. The same applies to glucoheptonic acid. The use concentration of the gluconic acid, glucoheptonic acid, salts thereof, lactones or mixtures thereof is 50 to 300 g/l,
Preferably 100-200f! /l is appropriate.

If the current density is less than 50 f1/l, the current density range for obtaining a dense plating film is narrow, and if it exceeds 3009 f1/l, no particular improvement in performance is observed and it is uneconomical.

The surfactant is effective in making precipitated particles finer and obtaining a dense plated film, and serves to suppress the occurrence of dendritic or spongy films, pits, pinholes, etc.

The anionic surfactant used in the present invention includes:
Polyoxyethylene alkyl ether sulfate is preferred, and the number of moles of ethylene oxide added is suitably 2 to 4. Examples of nonionic surfactants include polyoxyethylene alcohol ether, polyoxyethylene alkyl phenol ether, polyoxyethylene fatty acid ester,
Polyoxyethylene polypropylene block polymers are suitable, and in each case, the number of moles of ethylene oxide added is preferably 8 or more. This is because if it is less than 8, the water solubility is poor. As the cationic surfactant, polyoxyethylene aliphatic amine and polyoxyethylene aliphatic amide are preferred, and the number of moles of ethylene oxide added is 8? The above surfactants, which are preferred, can be used alone or in combination.

The concentration used is 0.05-209/l, preferably 1-10
9/' is appropriate. If it is less than 0.059/l, the effect of obtaining a dense plating film will not be sufficient, and if it exceeds 209/l, no improvement in the performance of the electrodeposited film will be observed, and the foaming property of the dazzling bath will be significant, making it inappropriate. Not.

By adding hydrazine or its salt, the oxidation of divalent tin to tetravalent tin is prevented, and the precipitation of a dendritic film is particularly suppressed in high current density areas, making it possible to obtain a dense plating film. .

Furthermore, passivation of the tin anode or the tin-lead alloy anode is prevented, and the solubility of the anode and the conductivity of the liquid are improved. The appropriate concentration of hydrazine or its salt is 2 to 1009/l, preferably 10 to 509/l. If it is less than 29/l, the effect is small, and if it exceeds 1009/l, no particular improvement in performance is observed.

When plating is performed using the plating bath of the present invention, the pH range is 2.0 to 10.01, preferably 3.0 to 10.01. O~7.0
is appropriate. When the pH is less than 2 or more than PHlO, it becomes difficult to obtain a dense plating film. For pH adjustment, sodium hydroxide, potassium hydroxide, aqueous ammonia, hydrochloric acid, sulfuric acid, nitric acid, etc. may be used as appropriate. The appropriate cathode current density is 0.1 to 6 A/d, preferably 1 to 3 A/d. Bath temperature is 20-60℃, preferably 30-60℃
55°C is suitable. For stirring, fluid stirring using a cathode rocker or the like is preferable; air stirring is inappropriate because the stannous salt is oxidized to the stannic salt. For the anode, tin is used for tin plating, and for tin-lead alloy plating, a tin-lead alloy anode having the same alloy composition as the electrodeposited film is used.

The tin and tin-lead alloy plating solution of the present invention is characterized in that wastewater treatment is easier than in conventional borofluorination baths, and the solution is not corrosive.

Since the plating solution of the present invention has excellent uniform electrodeposition properties, the plating film obtained using the solution is smooth, dense, and semi-gloss with no pits or pinholes. In tin-lead alloy plating, a plating film with the desired composition can be easily obtained by changing the metal concentration ratio in the solution, and there is little variation in the alloy composition of the plating film due to changes in current density. It has characteristics. Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A plating solution consisting of tinning was used to coat a copper plate at a temperature of 40°C.
Electricity was applied for 10 minutes at a current density of A/d to obtain a smooth, dense, white semi-glossy plating film.

Example 2 A plating liquid consisting of tinning was used to coat a steel plate at a temperature of 50°C.
Electricity was applied for 5 minutes at a current density of A/d to obtain a smooth, dense, white semi-glossy plating film.

Example 3 A plating solution consisting of a tin-lead alloy was used to coat a copper plate at a temperature of 50°C.
A current was applied for 20 minutes at a current density of A/Dm'' to obtain a smooth, dense, semi-gloss plating film.

The lead content in the electrodeposited film was 4001). Example
4. Electricity was applied to the tin-lead alloy plated plate for 10 minutes at a current density of 3 A/d to obtain a smooth, dense, semi-gloss plated film.

The lead content in the electrodeposited film is 28C! ). Example
5. A brass plate plated with copper at a temperature of 55°C using a plating solution consisting of a tin-lead alloy was energized for 15 minutes with stirring using a cathode rocker at a current density of 4A/Dm2.

A smooth, dense, semi-gloss plating film was obtained. The lead content in the electrodeposited film was 38%. Example 6 A plating solution consisting of a tin-lead alloy was used to coat a copper plate at a temperature of 30°C.
Electricity was applied for 15 minutes at a current density of A/d to obtain a smooth, dense, semi-gloss plating film.

The lead content in the electrodeposited film was 15%. Example 7 Using a plating solution made of a tin-lead alloy, a smooth, dense, semi-gloss plating film was formed by applying current to a steel plate at a current density of 2 A/d for 15 minutes at a temperature of 50°C. Obtained.

Claims (1)

[Claims] 1 (i) a stannous salt, or a stannous salt and a lead salt; (ii)
) at least one compound selected from the group consisting of gluconic acid, glucoheptonic acid, alkali metal salts thereof, gluconolactone, and glucoheptonolactone; and (
iii) Tin or tin-lead alloy plating solution 2 characterized by containing a surfactant Tin or tin-lead alloy according to claim 1, further containing hydrazine or a salt thereof Plating liquid.