JP2512499B2 - Tin-lead alloy plating solution - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tin-lead alloy plating solution, and in particular, a good tin-lead alloy plating film can be obtained with a uniform film thickness in a high current density region. And a tin-lead alloy plating solution capable of suppressing the oxidation of divalent tin ions to tetravalent.

(Prior Art) Since tin / lead alloy plating has good corrosion resistance and solderability, it is widely used as an industrial plating for electronic industrial parts such as weak electric parts and lead frames. As a plating solution used for such tin-lead alloy plating, a borofluoride bath has been mainly used, but in recent years, an organic acid bath that has few problems in terms of pollution prevention measures has been developed and put into practical use. There are also things.

Similar to tin plating, tin / lead alloy plating cannot be practically obtained as a resin-like or powder-like plating from a plating solution containing no additive. Organic additives such as gelatin, glue, and peptone are generally known as additives for the borofluoride bath. Further, as an additive for the organic acid bath, a nonionic surfactant such as a thiourea compound (Japanese Patent Publication No. 57-25636), a monoammonium salt, an imidazolinium salt, a cation such as ethylene oxide of styrenated phenol, etc. Surfactant (JP-A-59-67387), alkali metal of aromatic sulfonic acid (JP-B-60-9115), guanamine compound and the like (JP-A-61-48589), ethylene oxide adduct of ethoxylated α-naphthol Etc. (JP-A-61-73896), surface-active agents such as polyoxyalkylene alkylamines, ethylenediamine polyoxyalkylene adducts (JP-A-61-73896).
-117297) is known as a plating solution.

(Problems to be Solved by the Invention) In recent years, industrial tin-lead alloy plating is required to have the following characteristics. That is, as a tin-lead alloy plating solution, good plating can be performed at a higher current density, and the oxidation of Sn ²⁺ to Sn ⁴⁺ in the plating solution is as small as possible.

Moreover, the deposition ratio in the obtained tin-lead alloy plating film is constant, the solder wettability is good, and the plating film thickness is uniform.

However, when the above additives are used, the actual current density used is about 0.5 to 5.0 A / dm ² , and even if the plating conditions are set to a certain current density, the material to be plated is The locally observed current densities in the respective surface parts are not necessarily the same, and the distributions are non-uniform, which is particularly remarkable in the case of a material having a large plating area, a material having a complicated shape, or the like. As a result, the variation in plating film thickness becomes large. Therefore, it is required that the deposition rate be substantially constant in a wide current density range. Further, it is required that the solder wettability is good and the deposition rate in the plating film is constant. Further, when any of the above-mentioned additives is used, a phenomenon in which the liquid is turbid due to oxidation of Sn ²⁺ to Sn ⁴⁺ for several turns is observed. As a result, the proportion of Sn ^{4+ in} the plating solution increases and the deposition rate decreases.

Therefore, the object of the present invention is not only to be able to plate at a high current density, but in a wide current density range of the high current density region, the deposition ratio of the plating film is constant, and the deposition rate of the plating film is almost constant. A tin-lead alloy plating solution capable of obtaining a good quality tin-lead alloy plating film and suppressing the oxidation of Sn ²⁺ to Sn ⁴⁺ .

(Means for Solving Problems) As a means for solving the above problems, the present invention comprises 0.01 to 30 g / at least one kind selected from nonionic surfactants.
l, 0.01 to 30 g / l of at least one selected from cationic surfactants, at least selected from heterocyclic compounds having a nitrogen atom in the ring and a hydroxyl group bonded to the heterocycle and derivatives thereof It is intended to provide a tin-lead alloy plating solution containing 0.05 to 50 g / l of one type and 0.01 to 20 g / l of 1,4- or 1,7-dihydroxynaphthalene.

Non-ionic surfactants of the present _{invention, C n H 2n + 1 -C} 6 H 4 -
O- (C _m H _2m O) _k H (where n = 5 to 20, m = 2 to
3, k = 4 to 20), a polyoxyalkylene alkylphenol ether represented by the general formula, for example, polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether, polyoxyethylene oleylphenol ether, polyoxypropylene octylphenol ether, Examples thereof include polyoxypropylene nonylphenol ether.

Usually, one or two of these nonionic surfactants are used.
Seed or more is contained at a concentration of 0.01 to 30 g / l, preferably 0.3 to 1.5 g / l. These nonionic surfactants improve the appearance of precipitation and the throwing power. If it is less than 0.01 / l, gas pit unevenness is observed in the deposited film, resulting in poor appearance. Also, 30g /
When it is 1 or more, the throwing power and the deposition rate are lowered.

The cationic surfactant is a quaternary monoammonium salt, a quaternary diammonium salt, an alkylquinolinium salt, an alkylimidazolium salt or an alkylpyridinium salt, and examples thereof include lauryltrimethylammonium salt and octadecyltrimethylammonium salt. , Palm alkyl dimethyl benzyl ammonium salt, octadecyl dimethyl benzyl ammonium salt, N-beef tallow alkyl N, N,
N ', N', N'-pentamethyl propylene diammonium salt, coconut alkylisoquinolinium salt, coconut alkyl imidazolinium salt, octadecyl imidazolinium salt,
Hexadecyl pyridinium salt, tetradecyl pyridinium salt, etc. can be mentioned.

One or more of these cationic surfactants are contained in a concentration of 0.01 to 30 g / l, preferably 0.3 to 15 g / l. These cationic surfactants have the effect of improving the deposition state and the film appearance. If it is less than 0.01 g / l, resinous deposition and a black-gray coating with a poor appearance will result. In addition, when it is 30 g / l or more, unevenness is observed and the appearance of the deposited film becomes poor.

A heterocyclic compound having a nitrogen atom in the ring and a hydroxyl group bonded to the heterocycle and derivatives thereof will be described. The heterocyclic compound having a nitrogen atom in the ring as used herein is, for example, a compound such as pyridine, imidazole, quinoline or purine, and these may be substituted with alkyl or the like. The heterocyclic compound having a hydroxyl group bonded to the heterocycle used as the additive of the present invention is a compound having a hydroxyl group directly bonded to the above-exemplified heterocyclic compound having a nitrogen atom in the ring. Examples of such compounds include 2-oxypyridine, 2-oxyimidazole, quinulin, oxyquinaldine, 7-undecyl-8-quinolinol, 2-methyl-3-quinolinol, 8-oxyquinoline, 2,6-quinoline. Diol, 2,8-dihydroxyquinoline, 7-hydroxy-2-quinolone, 2-hydroxy-4-quinolinecarboxylic acid, 8-hydroxyquinoline-5-sulfonic acid, 2-methyl-8-hydroxyquinoline and salts thereof, etc. Can be mentioned. The content of the above-mentioned heterocyclic compound having a nitrogen atom in the ring and a hydroxyl group bonded to the heterocycle and the derivative thereof in the tin-lead alloy plating solution can be changed over a relatively wide range. From the viewpoint of the quality and productivity of the film used, 0.
05 to 50 g / l is preferable, and 0.3 to 20 g / l is particularly preferable. When the content is 0.05 g / l or less, it is difficult to obtain the effect of including the above compound and its derivative. That is, it is difficult to perform plating at a high current density, and the effect of preventing divalent tin ions from becoming tetravalent cannot be expected. On the other hand, when it exceeds 50 g / l, the cathode current density range has almost no effect on the appearance of precipitation, but the gas generation in the plating solution is intense, the cathode current efficiency becomes poor, and on the contrary, the deposition rate tends to be slow, It does not lead to productivity improvement.

1,4- or 1,7-dihydroxynaphthalene is 0.01 to 20
It is contained at a concentration of g / l, preferably 0.1-10 g / l. 0.01 g
If it is less than / l, it is difficult to obtain the effect of containing the above compound. That is, the effect of preventing the oxidation of divalent tin ions to tetravalent cannot be expected. On the other hand, when it exceeds 20 g / l, a black-grey precipitate film is obtained, resulting in poor appearance. Other isomers, 1,5-, 1,6
-, 2,3-, 2,7-dihydroxynaphthalene and the like are 1,4-
Or, the remarkable antioxidant effect of divalent tin ion to tetravalent, which is found in 1,7-dihydroxynaphthalene, is hardly recognized.

A nonionic surfactant, a cationic surfactant, and a heterocyclic compound having a nitrogen atom in the ring and a hydroxyl group bonded to the heterocycle contained in the tin-lead alloy plating solution of the present invention. , And 1,4- or 1,7-dihydroxynaphthalene, the white turbidity due to the formation of Sn ⁴⁺ was not observed for about 7 turns and the oxidation of divalent tin ion in the solution to tetravalent was suppressed. ,
High current density, ie 5 to 100A / at 30 ℃, total metal concentration 25g / l
In the dm ² (rack method), a tin-lead alloy plating film having a uniform deposition rate and a good deposition appearance can be obtained with a uniform film thickness.

The other components of the tin-lead alloy plating solution of the present invention are the same as those of the ordinary tin-lead alloy plating solution, and those obvious to those skilled in the art can be used. For example, borofluoric acid, or alkanesulfonic acid such as methanesulfonic acid and ethanesulfonic acid,
Alkanol sulfonic acids such as 2-hydroxyethane-1-sulfonic acid and 3-hydroxypropane-1-sulfonic acid, phenol sulfonic acid, etc., and borofluoride baths containing their divalent tin salts and lead salts as main components , An alkane or alkanol sulfonic acid bath and the like.

The tin-lead alloy plating solution according to the present invention can be used not only in the rack system but also in the jet system (high speed plating).

(Examples) Examples of the present invention are shown below, but the present invention is not limited to these examples, and the composition and conditions of the plating solution can be arbitrarily changed according to the purpose.

Example 1 Stannous methanesulfonate (as divalent tin) 17.5 g / l Lead methanesulfonate (as divalent lead) 7.5 g / l Free methanesulfonic acid 120 g / l Polyoxynonylphenol ether 1.5 g / l Plating solution containing N-beef tallow alkyl N, N, N ', N', N'-pentamethyl propylene diammonium dichloride 1.5g / l 8-oxyquinoline 15.0g / l 1,7-dihydroxynaphthalene 0.2g / l Was prepared, and the plating solution temperature was adjusted to 30 ° C. Next, while the plating solution was stirred using a magnetic stirrer, tin-lead alloy plating was performed by a rack method on the nickel-plated brass plate using the platinum-coated titanium mesh as an anode. Table 1 shows the deposition appearance of the tin-lead alloy plating film obtained at that time, the cathode current density range and the tin deposition ratio at which the alloy plating film having good semi-gloss can be obtained. In this good deposition appearance current density range, the deposition rate was 1.2 to 1.5 μm / min, which was a substantially constant value. The plating solution was ^turbid even after 6 turns due to the formation of S ^{4+, and} no formation of precipitate was observed.

Example 2 Stannous ethanesulfonate (as divalent tin) 18 g / l Lead ethanesulfonate (as divalent lead) 2 g / l Free ethanesulfonic acid 150 g / l Polyoxyoctylphenol ether 0.5 g / l Palm oil alkyl A plating solution containing isoquinolinium bromide 0.5 / l 2-methyl-8-hydroxyquinoline 10 g / l 1,7-dihydroxynaphthalene 3 g / l was prepared, and the plating solution temperature was adjusted to 60 ° C. Other than that, tin-lead alloy plating was performed under the same conditions as in Example 1. Table 1 shows the results. Good deposition appearance In the current density range, the deposition rate was 1.5 to 2.0 μm / min, which was almost constant. Further, this plating solution was ^turbid even after 7 turns due to the formation of Sn ^{4+, and} no formation of precipitate was observed.

Example 3 Stannous 3-hydroxypropane sulfonate (as divalent tin) 42 g / l Lead 3-hydroxypropane sulfonate (as divalent lead) 18 g / l Free 3-hydroxypropane sulfonate 120 g / l poly Oxyoleylphenol ether 5g / l N-beef tallow alkyl N, N, N ', N', N'-pentamethyl propylene diammonium dichloride 10g / l 8-hydroxyquinoline-5-sulfonic acid 5.0g / l 1,7- A plating solution containing 1.5 g / l of dihydroxynaphthalene was prepared, and tin-lead alloy plating was performed under the same conditions as in Example 1. The results are shown on the surface 1.
Good deposition appearance In the current density range, the deposition rate is 3.2 to 3.6.
It was a constant value of μm / min. In addition, this plating solution becomes cloudy due to the formation of Sn ⁴⁺ up to 6.5 turns,
No formation of precipitate was observed.

Example 4 Stannous methanesulfonate (as divalent tin) 17.5 g / l Lead methanesulfonate (as divalent lead) 7.5 g / l Free methanesulfonic acid 150 g / l Polyoxynonylphenol ether 1.5 g / l A plating solution containing lauryltrimethylammonium chloride 5.0 g / l 8-oxyquinoline 15.0 g / l 1,7-dihydroxynaphthalene 0.4 g / l was prepared, and tin-lead alloy plating was performed under the same conditions as in Example 1. did. Table 1 shows the results. Good deposition appearance Deposition rate is 1.1 to 1.4μ in the current density range.
The value was m / min, which was almost constant, but the appearance of precipitation was slightly gray. This plating solution is Sn up to 6 turns.
^The liquid was turbid due to the formation of ^{4+, and} the formation of a precipitate was not observed.

Example 5 Stannous 2-hydroxyethane sulfonate (as divalent tin) 18 g / l Lead 2-hydroxyethane sulfonate (as divalent lead) 2 g / l Free 2-hydroxyethane sulfonic acid 120 g / l poly A plating solution containing oxyoctylphenol ether 5 g / l 1-hydroxyethyl-2-alkylimidazolium chloride 2.5 g / l 8-oxyquinoline 1.0 g / l 1,7-dihydroxynaphthalene 0.5 g / l was prepared. Tin-lead alloy plating was performed under the same conditions as in 1. Table 1 shows the results. Good deposition appearance In the current density range, the deposition rate is 1.2 to 1.5μ
The value was m / min, which was almost constant, but the appearance of precipitation was slightly gray. This plating solution is Sn up to 6 turns.
^The liquid was turbid due to the formation of ^{4+, and} the formation of a precipitate was not observed.

Example 6 Stannous phenol sulfonate (as divalent tin) 17.5 g / l Lead phenol sulfonate (as divalent lead) 7.5 g / l Free phenol sulfonate 120 g / l Polyoxylauryl phenol ether 2.5 g / l N-beef tallow alkyl N, N, N ', N', N'-pentamethyl propylene diammonium dichloride 1.5 g / l 2-methyl-8-hydroxyquinoline 7.5 g / l 1,7-dihydroxynaphthalene 0.4 g / l A plating solution containing was prepared, and tin-lead alloy plating was performed under the same conditions as in Example 1. Table 1 shows the results. Good deposition appearance In the current density range, the deposition rate is 1.0 to 1.4μ
The value was almost constant at m / min. In addition, the plating solution was turbid due to the formation of Sn ⁴⁺ for 6 turns, and no formation of a precipitate was observed.

Example 7 Stannous borofluoride (as divalent tin) 18 g / l Lead borofluoride (as divalent lead) 2 g / l 100 g / l polyfluorononylphenol ether 10 g / l cocoalkylisoquinoli A plating solution containing 5 g / l of 8-nium bromide, 1.0 g / l of 8-oxyquinoline and 0.7 g / l of 1,4-dihydroxynaphthalene was prepared, and tin-lead alloy plating was performed under the same conditions as in Example 1. Table 1 shows the results. Good deposition appearance Deposition rate is 3.0-3.4μ in current density range
The value was almost constant at m / min. In addition, the plating solution was turbid due to the formation of Sn ⁴⁺ for 6 turns, and no formation of a precipitate was observed.

Example 8 In Example 1, instead of the platinum-coated titanium mesh, a 7: 3 solder plate and an 8-oxyquinoline content of 0.5 were used.
The tin-lead alloy plating was performed under the same conditions as in Example 1 except that g / l was used. Table 1 shows the results. Good deposition appearance In the current density range, the deposition rate was 3.1 to 3.6 μm / min, which was almost constant. Also, this plating solution is for up to 6 turns
No white turbidity due to the formation of Sn ⁴⁺ was observed.

Example 9 Under the same conditions as in Example 2, except that the platinum-coated titanium mesh was replaced by a 9: 1 solder plate and the content of 2-methyl-8-hydroxyquinoline was 1.0 g / l. Tin / lead alloy plating was applied. Table 1 shows the results.
Good deposition appearance In the current density range, the deposition rate is 3.2 to 3.7.
It was a constant value of μm / min. Further, this plating solution did not show white turbidity due to formation of Sn ⁴⁺ until 6 turns.

Comparative Example 1 Tin-based on the same conditions as in Example 1 except that polyoxynonylphenol ether was not used.
Lead alloy plating was applied. Table 1 shows the results. Unevenness due to gas pits was observed, and no current density range showing a good precipitation appearance was observed. The deposition rate was 1.2-1.4 μm / min in the current density range of 10-100 A / dm ² . In addition, this plating solution showed white turbidity due to the formation of Sn ⁴⁺ in about 6 turns.

Comparative Example 2 In Example 1, N-beef tallow alkyl N, N, N ', N',
Tin-under the same conditions as in Example 1 except that N'-pentamethylpropylenediammonium dichloride was not used.
Lead alloy plating was applied. Table 1 shows the results. Resinous precipitation was observed, and no current density range showing a good precipitation appearance was observed. The deposition rate was 1.2 to 1.5 μm / min in the current density range of 10 to 100 A / dm ² . In addition, this plating solution showed white turbidity due to the formation of Sn ⁴⁺ in about 6 turns.

Comparative Example 3 Tin-lead alloy plating was performed under the same conditions as in Example 1 except that 8-oxyquinoline was not used. Table 1 shows the results. Good deposition appearance In the current density range, the deposition rate was 0.4 to 1.8 μm / min. In addition, this plating solution was observed to be cloudy due to the formation of Sn ^{4+ after} about 5 turns.

Comparative Example 4 In the same manner as in Example 6, except that 2-methyl-8-hydroxyquinoline was not used, tin.
Lead alloy plating was applied. Table 1 shows the results. Good deposition appearance In the current density range, the deposition rate is 0.8 to 1.3 μm / mi
n. Also, this plating solution is Sn
White turbidity due to the formation of ⁴⁺ was observed.

Comparative Example 5 In Example 7, tin-lead alloy plating was performed under the same conditions as in Example 7, except that 8-oxyquinoline was not used. Table 1 shows the results. Good deposition appearance In the current density range, the deposition rate was 2.8 to 3.3 μm / min. In addition, this plating solution was observed to be cloudy due to the formation of Sn ^{4+ after} about 5 turns.

Comparative Example 6 Tin-lead alloy plating was performed under the same conditions as in Example 1 except that 1,7-dihydroxynaphthalene was not used. Table 1 shows the results. Good deposition appearance In the current density range, the deposition temperature was 1.2-1.5 μm / min. Further, in this plating solution, white turbidity due to the formation of Sn ⁴⁺ was recognized in about 4 turns.

Comparative Example 7 In Example 1, in place of 1,7-dihydroxynaphthalene, other isomers 1,5-dihydroxynaphthalene, 1,6
The tin-lead alloy plating was performed under the same conditions as in Example 1 except that 0.2 g / l of -dihydroxynaphthalene, 2,3-dihydroxynaphthalene or 2,7-dihydroxynaphthalene was used. Table 1 shows the results. Good deposition appearance In the current density range, the deposition temperature was 1.2-1.5 μm / min. Also,
In this plating solution, white turbidity due to the formation of Sn ⁴⁺ was recognized in about 4 turns.

Comparative Example 8 In Example 1, 8-oxyquinoline and 1,7-
Tin-lead alloy plating was performed under the same conditions as in Example 1 except that dihydroxynaphthalene was not used. Table 1 shows the results. Good deposition appearance In the current density range, the deposition temperature was 0.5-1.8 μm / min. Further, this plating solution was observed to become cloudy due to the formation of Sn ⁴⁺ in about 1 turn.

(Effect of the invention) The tin-lead alloy plating solution of the present invention can be used not only at high current densities, but also has a constant plating film deposition ratio in a wide current density range and a plating film deposition rate. Is almost constant, a tin-lead alloy plating film having a uniform film thickness can be formed on the surface of the material. In addition, since the oxidation of Sn ²⁺ to Sn ⁴⁺ in the tin-lead alloy plating solution can be suppressed, the precipitation rate does not significantly decrease. Therefore, the tin-lead alloy plating film obtained from the tin-lead alloy plating solution of the present invention has a uniform film thickness, good solderability, and the solution itself is very stable. As a result, productivity can be improved, and a high-quality tin-lead alloy plating film can be provided.

Claims (1)

(57) [Claims] 1. At least one selected from a nonionic surfactant is 0.01 to 30 g / l, at least one selected from a cationic surfactant is 0.01 to 30 g / l, and a nitrogen atom is contained in the ring. And at least one selected from the group consisting of heterocyclic compounds having a hydroxyl group bonded to a heterocycle and derivatives thereof.
~ 50 g / l and 1,4- or 1,7-dihydroxynaphthalene
A tin-lead alloy plating solution containing 0.01 to 20 g / l.