JPH079076B2 - Tin-lead alloy plating bath - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sulfonic acid bath for tin-lead alloy electroplating capable of providing a stabilized tin-lead alloy composition electrodeposit.

BACKGROUND ART As a tin-lead alloy plating bath, a borofluoride bath has hitherto been used, but various restrictions are imposed on the treatment of wastewater containing fluorine. From this viewpoint, a tin-lead alloy plating bath using an organic sulfonic acid having relatively low toxicity has been proposed. For example, JP-A-59-67387 and JP-A-59-182986.
No. 4,968,009, which describes a nonionic surfactant such as an alkylene oxide adduct of styrenated phenol (eg, polyoxyethylene tristyrylphenyl ether POETSPE) in an organic sulfonic acid bath and certain sulfanilic acid (eg, N-
(3-hydroxybutylidene-p-sulfuranilic acid HBPSA and / or triazine (eg 2,4-diamino-6- {2 '
Addition of additives such as -alkyl imidazolyl (1 ')} ethyl-1,3,5-triazine DAAIMET) gave a fine tin-lead alloy plating film with grayish white and uniform electrodeposit particles Is listed.

Tin-lead alloy (so-called solder) plating is widely used as a soldering film for light electrical parts and electronic industry parts, and lead is used in the range of several to 20% when whiskers are a problem.
The solder plating containing a certain amount is applied, and the solder plating containing 70 to 80% of lead is applied to those requiring corrosion resistance. As an etching resist for printed circuit boards, 60/40 eutectic solder plating is used.

As described above, solder plating requires a plating film having a different composition depending on its application, and it is ideal that an electrodeposit having a constant composition can always be obtained even if the current density changes from low current density to high current density. Is.

For example, tin-lead alloy plated printed circuit boards are generally subjected to a fusing treatment (melting treatment) to remove overhangs and improve solderability. At this time, if the compositions of the electrodeposits on the surface portion of the printed circuit board and the through-holes are different, the melting points of the electrodeposits on both portions are different, so that an uneven and rough fusing surface is produced. Therefore, when tin-lead alloy plating is applied to the printed circuit board, it is required that an electrodeposit having a uniform composition be attached from the surface of the board to the inside of the through hole.

Also, as tin-lead alloy plating for printed circuit boards,
In particular, semi-gloss plating is widely used because it does not require gloss in many cases, smooth and uniform electrodeposition is possible, and the fusing property is good.

The inventor has found that the lead content in the tin-lead alloy plating film from the conventional organic sulfonic acid bath tends to increase under low current density conditions, and thus the tin obtained under low current density conditions With respect to the lead alloy plating, it was found that a suitable Sn / Pb ratio could not be obtained, and the above-mentioned problems occur, and various auxiliary additives were investigated. As a result, some guanamine compounds have a constant Sn / Pb ratio not only under low current density conditions but also under high current density conditions, and
The present invention has been completed by finding that it provides a tin-lead alloy plating film having a Sn / Pb ratio substantially the same as the n / Pb ratio.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a tin-lead alloy plating bath capable of providing an electrodeposit having a constant Sn / Pb ratio not only under low current density conditions but also under high current density conditions. The purpose is to do.

DISCLOSURE OF THE INVENTION That is, the present invention is mainly composed of alkanesulfonic acid or alkanolsulfonic acid and their divalent tin salts and lead salts, to which a nonionic surfactant and / or a leveling agent are added. In the tin-lead alloy electroplating bath added, the following general formula is used as a stabilizer for the tin-lead precipitate composition. (Wherein, R ₁ and R ₂ may be the same or different, each a hydrogen atom, C ₁ ~ ₁₈ linear or branched alkyl group, C ₁ ~ ₁₈ linear or branched alkoxy - lower alkyl group or represents C ₃ ~ ₇ cycloalkyl group, or R ₁
And R ₂ together can form a piperidine, morpholine or piperazine ring, and A represents a lower alkylene group), and a granamine compound having a concentration of 0.01 to 30 g per bath liquid is added. And tin-
Lead alloy electroplating bath.

As a preferred guanamine compound that can be used, _one of R ₁ and R ₂ represents a hydrogen atom, the other C ₅ ~ ₁₄
Alkyl group (e.g. pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, etc.), C ₅ ~ ₁₄ alkoxy - ethyl or - propyl (e.g. pentyloxy -, hexyloxy -, heptyloxy -, octyloxy -, 2 -Ethylhexyloxy- or decyloxy-ethyl or -propyl etc.) or a cyclohexyl group, or R ₁ and R ₂ together are piperidine,
Examples thereof include those that form a morpholine or piperazine ring. Preferred lower alkylene groups are ethylene or propylene groups.

In the present invention, the guanamine compound is 0.01 to 1 per 1 bath liquid.
It is added in an amount of 30 g, preferably 0.1-10 g /.

The main plating bath of the present invention is basically an organic sulfonic acid,
That is, it is composed of at least one of alkanesulfonic acid or alkanolsulfonic acid and tin salt or lead salt of those sulfonic acids.

Alkane sulfonic acids or alkanol sulfonic acids that can be used are of the general formula:

[Where, R: C ₁ ~ ₁₂ alkyl group] _{R-SO 3 H HO-R} -SO 3 H [wherein, R: C ₁ ~ ₁₂ alkyl group, a hydroxyl group may be filed at an arbitrary position of the alkyl group ] Examples of alkanesulfonic acid include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, 2-probansulfonic acid, butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, decanesulfonic acid,
Dodecane sulfonic acid and the like. These alkanesulfonic acids can be used alone or as a mixture of two or more kinds.

Examples of alkanol sulfonic acids are isethionic acid (2-hydroxyethane-1-sulfonic acid), 2-hydroxypropane-1-sulfonic acid, 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid 2-hydroxybutane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-
They are 1-sulfonic acid and 2-hydroxydodecane-1-sulfonic acid. These hydroxy-containing alkanesulfonic acids can be used alone or as a mixture of two or more kinds.

The total concentration of tin and lead salts is 0.5 to 200 g /, in terms of metal.
It is preferably 10 to 100 g /. The concentration of alkane sulfonic acid or alkanol sulfonic acid present in the plating bath is 30 to 400 g /, preferably 70 to 150 g /.

According to the present invention, the S / Pb ratio in the plating bath is substantially the same as the S / Pb ratio.
A plated film having an n / Pb ratio can be obtained not only under low current density conditions but also over a wide current density range.

To the tin-lead alloy plating bath of the present invention, a surfactant, particularly a nonionic surfactant is added in order to improve the dispersibility of the plating bath and to obtain a smooth plating with good adhesion. To do. In particular, it has been found that the nonionic surfactant has an effect of improving throwing power at a low current density.

The nonionic surfactant that can be effectively used in the plating bath of the present invention is represented by the following general formula (I). (Wherein, RA is C ₈ ~ ₂₀ alkanol residues, residues of C ₁ ~ ₂₅ alkyl phenols, C ₁ ~ ₂₅ alkyl β- naphthol residue, residues of C ₃ ~ ₂₂ fatty acid amides, C ₁ ~ residues ₂₅ alkoxylated phosphoric acid, residues of sorbitan esters esterified with C ₈ ~ ₂₂ higher fatty acids, or styrenated phenol of (hydrogen phenol nuclei may be substituted with C ₁ ~ ₄ alkyl or phenyl) R'and R "represent a hydrogen atom or a methyl group, provided that R" represents a methyl group when R'represents a hydrogen atom and R "represents a methyl group when R'represents a methyl group. Represents a hydrogen atom, m represents an integer of 1 to 30, and n represents an integer of 1 to 30).

Nonionic surfactants of the formula which can be used for the plated bath (I) of the present invention shall apply well known in the art, well-known methods C ₃ ~ ₂₂ higher alcohols, alkyl phenols, alkyl β- naphthol, C ₃ to ₂₂ fatty acid amide, alkoxylated phosphoric acid, sorbitan esterified with C ₃ to ₂₂ higher fatty acid or styrenated phenol to be added and condensed with ethylene oxide (or propylene oxide), and further to be subjected to addition condensation with propylene oxide (or ethylene oxide) Can be manufactured by.

Examples of higher alcohols capable of addition-condensing ethylene oxide or propylene oxide include, for example, octanol, decanol, lauryl alcohol, tetradecanol, hexadecanol, stearyl alcohol,
Examples thereof include eicosanol, cetyl alcohol, oleyl alcohol, cetyl alcohol and docosanol. Alkylphenols include mono-, di- or tri-alkyl substituted phenols such as p-butylphenol, p-isooctylphenol, p-nonylphenol,
p-hexylphenol, 2,4-dibutylphenol, 2,4,
6-tributylphenol, p-dodecylphenol, p-laurylphenol, p-stearylphenol and the like can be mentioned. Examples of the alkyl group of alkyl β-naphthol include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, octadecyl and the like, which may be located at any position on the naphthalene nucleus. Examples of fatty acid amides include amides such as propionic acid, butyric acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. The alkoxylated phosphoric acid has the formula (Where Ra is Rb: C ₁ ~ ₂₅ alkyl group, and one of which,
It may be one hydrogen atom). That is obtained by esterification with alcohols having 1 or 2 hydroxyl groups suitable chain length of the phosphate (C ₁ ~ _25). Styrenated phenol has the following formula (Where Rc: hydrogen, C ₁ ~ ₄ alkyl group or phenyl group x: 1 to 3) mono represented by -, di - or tri styrenated phenol can be mentioned, C ₁ ~ ₄ alkyl groups in the phenol nucleus Alternatively, a phenyl group may be substituted. Suitable examples include mono-, di- or tri-styrenated phenol, mono- or di-styrenated cresol, mono- or di-styrenated phenylphenol and the like. It may be a mixture of these. Sorbitans esterified with higher fatty acids include mono-, di- or tri-esterified sorbitan
4-, 1,5 and 3,6-sorbitan, for example sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan oleate, sorbitan dilaurate, sorbitan dipalmitate, sorbitan distearate, sorbitan dioleate , Sorbitan mixed fatty acid ester and the like.

The above nonionic surfactants can be used alone or in combination.

The concentration of the nonionic surfactant used is generally 0.01 to
It is 50 g /, preferably 0.03 to 20 g /.

Further, the plating bath of the present invention contains certain smoothing additives to improve the smoothness of the plating surface. The smoothing additive has a further synergistic effect by being used in combination with the above-mentioned surfactant. Examples of smoothing additives that have been found to be particularly effective include those having the following general formulas (A) to (B).

[Wherein, Rc: hydrogen, C ₁ ~ ₄ alkyl group or a phenyl group, Rd: hydrogen or hydroxyl, B: C ₁ ~ ₄ alkylene group, phenylene group or a benzyl group Re: hydrogen or C ₁ ~ ₄ alkyl group] _{[Wherein, Rf, Rg: C 1 ~} 18 alkyl group] Among these smoothing additives, in particular, N- (3- hydroxybutylidene)-p-Surufuaniru acid, N- blanking dust dense Ruff anil acid, N -Cinnamoylidene sulfanilic acid, 2,4-
Diamino-6- [2'-methylimidazolyl (1 ')] ethyl-1,3,5-triazine, 2,4-diamino-6- [2'-ethyl-4-methylimidazolyl (1')] ethyl- 1,3,5-
Examples thereof include triazine and 2,4-diamino-6- [2'-undecylimidazolyl (1 ')] ethyl-1,3,5-triazine.

The concentration of the smoothing additive is 0.01 to 30 g /, preferably 0.03 to
It is 5g /.

The concentration of each of the above-mentioned components of the plating bath of the present invention can be arbitrarily selected corresponding to barrel plating, rack plating, high-speed continuous plating, through-hole plating, and the like.

Further, the plating bath of the present invention can obtain a homogeneous and dense plating over a wide range of current densities.

Next, the composition of the plating solution and plating working conditions according to the examples of the present invention will be shown, but the present invention is not limited to these several examples, and the composition of the plating bath and the plating conditions can be arbitrarily set in accordance with the above-mentioned object. Can be changed.

Example 1 In the following example, various guanamine compounds described in Table-1 were added to a tin-lead alloy plating bath having the basic bath composition shown in Table-2, and plating was performed on a copper piece.

The plating was performed by constant current electrolysis of 600 coulomb at a predetermined current density while moving the cathode at 2 m / min using a copper wire of φ2 mm × 200 mm as a cathode. The obtained electrodeposit was dissolved in 6N-HC1 and the lead content (%) in the electrodeposit was determined by atomic absorption spectrometry.
Was measured. The measurement results are shown in FIG.

Example 2 A tin-lead alloy-plated sample obtained from a bath obtained by adding each stabilizer of Table 1 to the basic bath of Table-2 was subjected to infrared ray fusing treatment, and then the surface condition with respect to the fusing temperature was evaluated. The plating was performed under a relatively constant current density condition (0.25 A / dm ² ), the plating thickness was 10 μm, and the heating time of the fusing was constant at each predetermined temperature for 3 seconds.

Near-infrared surface heating device, automatic SC for fusing test
Using an R power controller and a temperature controller, the plated sample was set on a copper plate for temperature control connected with an iron-constantan thermocouple and irradiated with infrared light from the vertical direction.

The obtained results are shown in FIG.

As for the fusing property, it is desirable that the melting point be completely melted at a relatively low temperature, and therefore, in the case where the stabilizer was added, the completely melted surface was obtained in each case when compared with the basic bath.

Example 3 A tin-lead alloy plating film was formed from a bath having the following composition, the relationship between the current density and the lead content in the electrodeposit was determined, and the fusing property was evaluated.

2-Hydroxypropanesulfonic acid first tin (as divalent tin) 12g / 2-hydroxypropanesulfonic acid lead (as divalent lead)
8 Free methanesulfonic acid 100 C ₂ C ₆ OPAA 2 The results are shown in FIGS. 3 and 4. Even with C ₂ C ₆ OPAA alone, the electrodeposition composition was stable, and the fusing property was also stable.

Example 4 By adding each stabilizer of Table-1 to the basic plating bath shown in Table-3, the alloy composition of the tin-lead alloy electrodeposit obtained from the plating bath was prepared in the same manner as in Example-1. It was measured. The results are shown in Table-4
Shown in.

Example 5 The alloy composition of the tin-lead alloy electrodeposit obtained from the dipping bath by adding the stabilizers of Table 1 to the basic dipping bath shown in Table 5 was carried out in the same manner as in Example 1. It was measured. The results are shown in Table-6
Shown in.

Example 6 By adding each stabilizer of Table 1 to the basic plating bath shown in Table 7, the alloy composition of the tin-lead alloy electrodeposit obtained from the plating bath was prepared in the same manner as in Example 1. It was measured. Table-8 results
Shown in.

Example 7 The alloy composition of the tin-lead alloy electrodeposition obtained from the plating bath by adding each stabilizer of Table 1 to the basic plating bath shown in Table 9 was the same as in Example 1. It was measured. The results are shown in Table-10.
Shown in.

Example 8 By adding each stabilizer of Table-1 to the basic plating bath shown in Table-11, the alloy composition of the tin-lead alloy electrodeposit obtained from the plating bath was prepared in the same manner as in Example-1. It was measured. The results are shown in Table-12.
Shown in.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship of the lead content in the electrodeposit according to the change in current density in tin-lead alloy plating using various guanamine compounds. FIG. 2 is a diagram showing a surface state of a tin-lead alloy plated film using various guanamine compounds after the fusing. FIG. 3 is a graph showing the relationship between the lead content in the electrodeposit and the change in current density in another specific example. FIG. 4 is a view showing the surface state of the tin-lead alloy plated coating of another specific example after the fusing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keigo Obata 1-8 Kourigicho, Himeji City, Hyogo Prefecture (72) Inventor Nobuyasu Doi 1-4-4 Tsukimiyamamotomachi, Suma-ku, Kobe City, Hyogo Prefecture (72) Inventor Oku Yoshiaki Hama 6-5-17 Okamoto Higashi-Nada-ku, Kobe City, Hyogo Prefecture Okamoto Excel No. 502 (72) Inventor Seiji Masaki 4-16-5 Nishiyama-cho, Nagata-ku, Kobe City, Hyogo Prefecture (72) Yukino Okada Kobe, Hyogo Prefecture 4-1-1 Izumidai, Kita-ku, Kita-ku (72) Inventor Tadashi Yoshida 4-4-2, Tsukushigaoka, Kita-ku, Kobe-shi, Hyogo (56) Reference JP-A 59-182986 (JP, A) JP-A 59- 67387 (JP, A)

Claims (4)

[Claims] 1. An alkane sulfonic acid or alkanol sulfonic acid, and a divalent tin salt and a lead salt thereof as main components, to which a nonionic surfactant and / or a leveling agent are added. In the tin-lead alloy electroplating bath, the following general formula is used as a stabilizer for the tin-lead precipitate composition. (Wherein, R ₁ and R ₂ may be the same or different, each a hydrogen atom, C ₁ ~ ₁₈ linear or branched alkyl group, C ₁ ~ ₁₈ linear or branched alkoxy - lower alkyl group or represents C ₃ ~ ₇ cycloalkyl group, or R ₁
And R ₂ together can form a piperidine, morpholine or piperazine ring, where A represents a lower alkylene group), and was added at a concentration of 0.01 to 30 g per liquor of a bath of a guanamine compound. And tin-
Lead alloy electroplating bath. 2. A general alkane sulfonic acid and alkanol sulfonic acid of the following respective formulas R-SO ₃ H (wherein, R represents a C ₁ ~ ₁₂ alkyl _{group) HO-R-SO 3 H} ( wherein, R C ₁ ~ represents an ₁₂ alkyl group, a hydroxyl electroplating bath claims preceding claim, characterized in that it comprises a a may) at any position of the alkyl group. 3. The tin-lead salt of alkane sulfonic acid or alkanol sulfonic acid is converted to metal per 1 liquid of the bath.
The electroplating bath according to claim 1, which is used in a concentration of 0.5 to 200 g. 4. The electroplating bath according to claim 1, wherein the alkanesulfonic acid or the alkanolsulfonic acid is used in a concentration of 30 to 400 g per 1 liquid of the bath.