JP2709510B2 - Tin, lead, tin-lead alloy electroplating bath and electroplating method - Google Patents

Description

The present invention relates to a novel tin-lead alloy electroplating bath and an electroplating method using the bath.

[Prior Art and Problems to be Solved by the Invention] Tin, tin-lead alloy electroplating has been widely used in the field of light electric and electronics industries mainly for solderability.

Conventionally, an electroplating bath used for such tin, tin-lead alloy electroplating is mainly a sulfuric acid bath, an organic sulfonic acid bath or a borofluoric acid bath, and is a strongly acidic bath having a pH of 1 or less.

There is no particular problem in using these strongly acidic baths when the object to be plated is copper, steel, or the like. Recently, however, there have been many electronic components made of composite materials using metals and ceramics, glass, plastics, and the like as materials to be plated. For example, cerdip type IC packages sealed with lead glass, Chip capacitors are being used. Further, an increasing number of electronic components have been formed by depositing aluminum on ceramic and etching to form a circuit. When these parts are plated with tin or tin-lead alloy from the above-mentioned strong acid bath, the ceramic, glass or vapor-deposited aluminum in the parts is eroded, and furthermore, there is a problem that a bridge problem that plating is applied on an insulator occurs. there were.

Such a problem can be solved by adjusting the pH of the plating bath to 2 to 9. However, simply increasing the pH of the plating bath to 2-9
In this case, tin ions and lead ions precipitate as hydroxides, making plating impossible.

On the other hand, conventionally, as a tin, tin-lead alloy electroplating bath,
Various baths using citric acid, gluconic acid, pyrophosphoric acid, organic phosphonic acid, salts thereof and the like which can be used in the above pH range have been proposed (JP-A-49-93236, JP-A-53-5034).
Nos. 54-60230, 54-69533, 54-69534,
Nos. 57-63689, 61-194194, etc.), and a pH of 2 to
A plating bath capable of satisfactorily performing tin-lead alloy plating in region 9 is desired.

The present invention has been made in view of the above circumstances, and has a pH of 2 to 9.
It is an object of the present invention to provide a tin-lead alloy plating bath which is stable in the above-mentioned region, has high current efficiency, and can be used in a wide current density range, and an electroplating method using the plating bath.

[Means and actions for solving the problem]

The present inventors have conducted intensive studies to achieve the above object, and as a result, ascorbic acid, isoascorbic acid, dehydroascorbic acid, and ascorbic acid as complexing agents for a plating bath containing 1 to 100 g / tin ion and lead ion. By using one or more of the salts selected from the group consisting of 40 to 400 g / stable, it is stable in the pH range of 2 to 9 and does not generate hydroxides of tin or lead. Baths containing these complexing agents have high current efficiency, can be used in a wide range of current densities, and provide good plating films. The inventors have found that they can be obtained, and have accomplished the present invention.

Therefore, the present invention, 1 to 100 g of tin ions and lead ions
/ One or more selected from ascorbic acid, isoascorbic acid, dehydroascorbic acid and salts thereof as a complexing agent in a tin-lead alloy plating bath containing
A tin-lead alloy electroplating bath characterized by being mixed at 400 g / pH and having a pH of 2 to 9, and a tin characterized by electroplating an object to be plated using the plating bath.
A lead or tin-lead alloy electroplating method is provided.

 Hereinafter, the present invention will be described in more detail.

In the plating bath of the present invention, the metal salt that gives tin ions or lead ions is not particularly limited.
Examples include tin sulfate, tin chloride, tin nitrate, tin methanesulfonate, tin alkanolsulfonate, tin phenolsulfonate, tin borofluoride, tin acetate, and tin oxide. in this case,
The tin salt may be a divalent tin salt or a tetravalent tin salt. On the other hand, examples of the lead salt include lead nitrate, lead acetate, lead borofluoride, lead methanesulfonate, lead chloride, lead sulfate, and lead oxide.

The concentration of the above tin ions and lead ions in the plating bath is 1 to 10
0 g /.

The present invention provides ascorbic acid, isoascorbic acid,
One or more selected from dehydroascorbic acid and salts thereof are blended. In addition, examples of the salt include an alkali metal salt, an ammonium salt, a tin salt, and a lead salt.

 The addition amount of these complexing agents is 40 to 400 g /.

In the plating bath of the present invention, other complexing agents such as citric acid, pyrophosphoric acid, gluconic acid and salts thereof may be added in addition to the above complexing agents.

If necessary, a conductive salt, a pH buffer, a surfactant, a brightener and the like can be further added to the plating bath of the present invention.

Here, as the conductive salt, ammonium methanesulfonate, ammonium sulfate, ammonium chloride, sodium sulfate, potassium chloride, ammonium acetate, ammonium ascorbate, sodium alkanolsulfonate, sodium phenolsulfonate and the like can be used. The addition can lower the plating voltage and improve the throwing power. The blending amount can be 0 to 800 g /, preferably 10 to 800 g /
, More preferably 50 to 300 g /.

Examples of the pH buffer include boric acid, ammonium chloride, ammonium sulfate, ammonium acetate, sodium phosphate, potassium phosphate, sodium borate, potassium borate, sodium formate, potassium formate, ammonium citrate, sodium citrate and the like. No. The addition amount is preferably 0 to 100 g /, particularly preferably 10 to 50 g /.

Furthermore, nonionic, cationic, and
Zwitterionic or anionic surfactants can be used.
In this case, these surfactants are not particularly limited and variously selected, but those having a high cloud point or those having no cloud point are preferable from the viewpoint of salting out.

More preferably, nonionic surfactants obtained by adding 15 mol of ethylene oxide to nonylphenol, alkyl β-naphthol (alkyl group having 1 to 1 carbon atoms)
25) to which 25 mol of ethylene oxide is added, and polynuclear phenol ethoxylates (for example, Adecitol PC-10 and PC-13 manufactured by Asahi Denka Kogyo KK) and the like. Also,
As the cationic surfactant, those obtained by adding 10 mol of ethylene oxide to laurylamine, those obtained by adding 15 mol of ethylene oxide to tallow alkylamine, and the like are suitably used. Further, as the zwitterionic surfactant, imidazoline-based surfactants, in particular, the following formula (However, R ¹ is an alkyl group having 3 to 25 carbon atoms, and R ² is an alkyl group having 1 carbon atom.
(For example, Amogen No. 8 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is preferable.

The addition of the above-mentioned nonionic, cationic and amphoteric surfactants has the effect of smoothing and densifying the plating film, but the addition amount of these surfactants is 0.01 to 30 g /
It can be.

On the other hand, anionic surfactants have the effect of particularly eliminating gas pits in plating and increasing the cloud point of nonionic surfactants. Examples of anionic surfactants include sodium lauryl sulfate, sodium alkylbenzenesulfonate, and sulfosiloxane. Acid alkyl ester or the following formula (However, n = 2 to 5, m = 1 to 4), for example, sodium catechol disulfonate is preferably used. In addition, the addition amount of the anionic surfactant can be 0.1 to 50 g /.

When bright plating is required, a brightening agent is added. Examples of brightening agents include aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, glyoxal, succinaldehyde, caproaldehyde, and aldol, benzaldehyde, and salicylaldehyde aryl ether. , p-Tolualdehyde, 1-naphthaldehyde, salicylaldehyde, veratraldehyde, anisaldehyde, piperonal, vanillin and other aromatic aldehydes can be used. Further, sulfanilic acid derivatives,
Triazine derivatives, acrylic acid, methacrylic acid, crotonic acid, and other α-unsaturated carboxylic acids can also be used. The addition amount of these brighteners is 0.01 to 30 g /,
In particular, it can be 0.03 to 5 g /.

The plating bath of the present invention has a pH of 2 to 9, preferably 3 to 8.5, and more preferably 5 to 8.
In this case, ammonia water, caustic, or the like can be used to adjust the pH.

When performing electroplating using the above-mentioned plating bath, the power source is such that when a matte or semi-glossy plating film is obtained, the appearance of the plating film (parts where plating crystals become large and the parts become black) is considered. Full DC, three-phase full wave,
It is recommended to use single-phase full-wave or single-phase half-wave rectification rather than three-phase half-wave rectification, and a pulse power supply or the like is also used. on the other hand,
When obtaining a bright plating film, conversely, a single-phase full-wave
It is recommended to use full DC, three-phase full-wave, three-phase half-wave rectification rather than single-phase half-wave rectification.

The plating bath of the present invention can be used not only for ordinary rack plating, but also for barrel plating, and can also be applied to high-speed plating, through-hole plating, and the like. Plating conditions are selected according to the type of plating and the like. According to the plating bath of the present invention, a uniform and dense plating film can be obtained over a wide range of current densities. In particular,
The plating temperature can be 5 to 90 ° C., more preferably 10 to 60 ° C., and the cathode current density can be 0.001 to 30 A / dm ² , more preferably 0.1 to 10 A / dm ² . In addition, agitation, barrel rotation, cathode locking, pump flow,
It can be performed by liquid flow, air agitation or the like by supercooling, and in some cases, no agitation may be used. Depending on the type of plating bath, metallic tin, metallic lead, or, in the case of tin-lead alloy plating, a combination of metallic tin and metallic lead or a tin-lead alloy depending on the composition of the plating film However, an insoluble anode may be used.

In the present invention, the object to be plated is not limited and may be any as long as it can be electroplated. In particular, the present invention is suitable for plating of electronic components made of a composite material of metal and ceramic, glass, and the like. It is.

Hereinafter, the present invention will be described in detail with reference to Examples,
The present invention is not limited to the following examples.

[Example 1] Stannous methanesulfonate (as Sn) 10 g / lead methanesulfonate (as Pb) 1 ア ス ascorbic acid 200 〃 boric acid 30 エ チ レ ン ethylene oxide 15 mol adduct of tallowamine 1 〃 methanesulfonic acid 100 〃 pH using a plating bath 7 above composition (adjusted with aqueous ammonia), 40 ° C. on a copper plate by single-phase full-wave rectification, and plated for 10 minutes under the conditions of D _K 1A / dm ^2.

As a result, a smooth dense white semi-gloss tin-lead alloy plating film was obtained. The Pb content in the film was 10%, and the current efficiency was 99%.

Note that D _K 1A / d
Although plating of about 7 μm was performed at m ² , a tin-lead alloy plating film having a good white semi-gloss was obtained without attacking the lead glass.

In addition, after performing a zinc substitution treatment on a ceramic plate having an aluminum vapor-deposited film by a conventional method, a 10 μm tin-lead alloy plating was performed using the above plating bath, but without dissolving and eroding the vapor-deposited aluminum. Then, a tin-lead alloy plating film was formed on the evaporated aluminum with good adhesion.

[Example 2] Stannous sulfate (as Sn) 10 g / lead methanesulfonate (as Pb) 1 〃 dehydroascorbic acid 200 〃 boric acid 30 エ チ レ ン ethylene oxide 15 mol adduct of tallowamine 1 g / ammonium sulfate 50 〃 pH ( (Adjusted with ammonia water) 7 Plating was performed in the same manner as in Example 1 using the plating bath having the above composition, and the same result as in Example 1 was obtained.

Example 3 In the plating bath of Example 1, plating was performed using isoascorbic acid instead of ascorbic acid, and the same results as in Example 1 were obtained.

〔The invention's effect〕

According to the present invention, a good tin, lead, or tin-lead alloy plating film is provided in the pH range of 2 to 9, and the current efficiency is high, and it can be used in a wide current density range. It is preferably used.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kiyoshi Asakawa 1-5-1, Hirakata-shi, Osaka Pref. Uemura Kogyo Co., Ltd., Central Research Laboratory (56) References JP-A-62-270793 (JP, A) JP-A-62-27091 (JP, A) JP-A-63-128194 (JP, A) JP-A-1-96392 (JP, A) JP-A-50-118943 (JP) JP-A-47-33732 (JP, A) JP-B-55-29159 (JP, B2) JP-B--40-25483 (JP, B1)

Claims (2)

(57) [Claims] 1. One or two selected from ascorbic acid, isoascorbic acid, dehydroascorbic acid and salts thereof as a complexing agent in a tin-lead alloy plating bath containing 1 to 100 g / tin ions and lead ions. More than seeds 40-400g /
A tin-lead alloy electroplating bath characterized by being blended and having a pH of 2 to 9. 2. A method for electroplating a tin-lead alloy, comprising electroplating an object to be plated using the plating bath according to claim 1.