KR20150110184A - Electroless tin plating solution and method for electroless tin plating using the same - Google Patents

Abstract

The present invention relates to an electroless tin plating solution and to an electroless tin plating method using the same and, more specifically, relates to an electroless tin plating solution and an electroless tin plating method using the same, wherein dam damage between a copper plate and ink mounted thereon is mitigated during the electroless tin plating of a printed circuit board. For this purpose, the electroless tin plating solution in accordance to the present invention comprises: a first tin (Sn^2+); an electrolyte; a complexing agent; a surface active agent; and an antioxidant.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless tin plating solution and an electroless tin plating solution using the electroless tin plating solution,

The present invention relates to an electroless tin plating solution and a method of electroless tin plating using the electroless tin plating solution. More particularly, the present invention relates to an improvement of dam damage between a copper plate and a mounted ink during electroless tin plating of a printed circuit board, And an electroless tin plating method using the electroless tin plating solution.

In general, solder balls, which have been used for mounting IC chips on metal substrates such as copper substrates, have been replaced by precision plating for the purpose of cost reduction as well as trend toward higher densification and thinning of substrates.

 The tin plating layer is formed on the substrate by electrolytic plating. When the electrolytic plating method is used, the thickness of the plating may be uneven due to the non-uniformity of the current density on the substrate. Which is disadvantageous in terms of reliability of the entire product. Therefore, a method of plating tin on a metal product by electroless plating is used instead of electrolytic plating. In case of electroless plating, the plating performance is high, and the plating film becomes dense and uniform, and the quality of the whole product can be improved.

In the electroless plating method, there is an electroless substitution plating method in which a metal atom of a substrate to be plated transfers electrons to tin ions in a solution, and metal ions are eluted into a solution and tin ions are electrodeposited (plated) on the surface.

Substitution plating is in accordance with the following (1)

Sn ²⁺ + 2Cu? Sn + 2Cu ⁺ (1)

However, substitution plating causes dam damage due to active substitution at the interface between the ink and the copper layer, which makes it difficult to manufacture a printed circuit board requiring high reliability. To address this problem, it is required to develop ink and tin plating solution for preventing dam damage in displacement plating.

It is an object of the present invention to provide an electroless tin plating solution for improving and preventing dam damage caused by electroless tin plating of a printed circuit board, Tin plating method.

These and other objects and advantages of the present invention will become more apparent from the following description of a preferred embodiment thereof.

The above object is achieved by an electroless tin plating solution of the present invention.

The electroless tin plating solution of the present invention may contain a first tin (Sn ²⁺ ), an electrolyte, a complexing agent, a surfactant, and an antioxidant, and the complexing agent may include a carboxylic acid, a thiourea and a thiourea derivative .

The content of the first tin (Sn ²⁺ ) may be 7 to 15 g / L based on 1 L of the entire electroless tin plating solution.

The content of the electrolyte may be 40 to 200 g / L.

The complexing agent may have a weight ratio of thiourea: thiourea derivative of 5 to 7: 3 to 5 and a total content of 50 to 800 g / L.

The content of the surfactant may be 0.01 to 50 g / L.

The content of the antioxidant may be 0.01 to 20 g / L.

The source of the first tin (Sn ²⁺ ) may be at least one selected from the group consisting of tin methanesulfonate, tin sulfate, tin sulfamic acid and tin pyrophosphate.

The electrolyte may be at least one selected from the group consisting of methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid and 1-butanesulfonic acid as the alkanesulfonic acid.

The carboxylic acid of the complexing agent may be at least one selected from the group consisting of oxycarboxylic acid, polycarboxylic acid, monocarboxylic acid and salts thereof, more preferably gluconic acid, citric acid, glucoheptonic acid, It may be at least one selected from the group consisting of gluconolactone, glucoheptolactone, formic acid, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid, malonic acid, malic acid, tartaric acid, diglycolic acid and salts thereof.

The thiourea derivative of the complexing agent may be at least one selected from the group consisting of 1,3-dimethyl thiourea, trimethyl thiourea, diethyl thiourea, N, N-diisopropyl thiourea, allyl thiourea, acetyl thiourea, A 3-diphenylthiourea, and a thiourea dioxide.

The surfactant may be at least one selected from the group consisting of nonionic, anionic, cationic and amphoteric surfactants. The nonionic surfactant is selected from the group consisting of C ₁ to C ₂₀ alkane, C ₁ to C ₂₀ alkanol, phenol, naphthol, bisphenols, C ₁ to C ₂₅ alkylphenol, arylalkylphenol, C ₁ to C ₂₅ alkylnaphthol, At least one selected from the group consisting of C ₂ to C ₂₅ alkoxyphosphoric acid (salts), sorbitan esters, polyalkylene glycols, or C ₁ to C ₂₂ aliphatic amide condensed with about 2 to 300 moles of ethylene oxide or propylene oxide Lt; / RTI > The anionic surfactant may be at least one selected from the group consisting of alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, and alkylbenzenesulfonates. The cationic surfactant may be at least one selected from the group consisting of mono to trialkylamine salts, dimethyl dialkylammonium salts and trimethylalkylammonium salts. The amphoteric surfactant may be at least one selected from the group consisting of carboxybetaine, sulfobetaine, imidazolinebetaine and amicarboxylic acid.

Wherein the antioxidant is at least one compound selected from the group consisting of hydroquinone, catechol, resorcin, prorolysine, hydrazine, hypophosphorous acid, ascorbic acid, cresol sulfonic acid, phenolsulfonic acid, catechol sulfonic acid, hydroquinone sulfonic acid, .

According to another aspect of the present invention, there is provided an electroless tin plating method including electroless tin plating using the electroless tin plating solution.

According to the present invention, dam damage caused by electroless plating of a printed circuit board can be improved and prevented. Therefore, high reliability of the printed circuit board can be ensured.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

FIG. 1 is a view showing a dam damage occurrence position occurring during electroless replacement plating of a printed circuit board. FIG.
Fig. 2 is a diagram showing that dam damage of the sixth embodiment does not occur. Fig.
Fig. 3 is a diagram showing dam damage occurring in Comparative Example 1; Fig.
4 is a graph showing plating thicknesses according to Examples and Comparative Examples. Thickness cut line is 0.5 μm minimum thickness required by plating company.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. It will be apparent to those skilled in the art that these embodiments are provided by way of illustration only for the purpose of more particularly illustrating the present invention and that the scope of the present invention is not limited by these embodiments .

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

The electroless tin plating solution of the present invention includes first tin (Sn ²⁺ ), an electrolyte, a complexing agent, a surfactant, and an antioxidant.

In the present invention, a first tin salt soluble in water is used as the first tin (Sn ²⁺ ) source, and as a specific example, a tin salt selected from the group consisting of tin methanesulfonate, tin sulfate, tin sulfamate and tin pyrophosphate Is preferable. The amount of the first tin (Sn ²⁺ ) is preferably 7 g / L to 15 g / L. If the amount of the first tin (Sn ²⁺ ) is less than 7 g / L, the plating rate is lowered and the industrially required productivity is not satisfied, as well as the smoothness and film uniformity of the tin plating layer are impaired. When the amount of the first tin (Sn ²⁺ ) is more than 15 g / L, the amount of tin in the plating solution becomes large, so that precipitation of tin oxide can not be avoided. In order to produce industrially, it is usual that there is a certain level of fluctuation depending on the plating conditions when the first tin salt is used, and considering the unavoidable fluctuation that can not be managed by the plating condition forms a tin plating layer of more stable quality It is because.

Examples of the alkanesulfonic acid used as the electrolyte include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid and pentanesulfonic acid. These alkanesulfonic acids may be used alone or in combination of two or more. Among them, methanesulfonic acid is preferable. The amount of the alkanesulfonic acid added is preferably 40 to 200 g / L. When the added amount of the alkanesulfonic acid is less than 40 g / L or more than 200 g / L, not only the thickness of the electroless tin plating is thin but also the thickness of the plating is unevenly formed.

The complexing agent can be classified into a deposition agent and a secondary complexing agent. The adsorbing agent can serve as a complexing agent alone, but the auxiliary complexing agent can not serve as a complexing agent on its own. Examples of the covalent agent include thio urea and thiourea derivatives. Specifically, thiourea derivatives include 1,3-dimethyl thiourea, trimethyl thiourea, diethyl thiourea, N, N-diisopropyl thiourea, , Acetyl thiourea, ethylene thiourea, 1,3-diphenyl thiourea, thiourea dioxide and the like. The auxiliary complexing agent may be an oxycarboxylic acid, a polycarboxylic acid, a monocarboxylic acid or a salt thereof as a carboxylic acid. Specific examples thereof include gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptolactone, Formic acid, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid, malonic acid, malic acid, tartaric acid, diglycolic acid or salts thereof.

As the complexing agent, it can be used alone or in combination with the auxiliary complexing agent. However, damaging may occur when the electrolessly tin plating is performed by using the deposition agent alone. However, when the thiourea and the thiourea derivative are mixed with the carboxylic acid as the auxiliary complexing agent and the following contents are used, the dam damage can be improved.

The total content of the complexing agent is 50 to 800 g / L, and when the weight ratio of the thiourea and the thiourea derivative alone is compared, it is preferable that the thiourea: thiourea derivative is mixed at 5 to 7: 3 to 5. If the total content or the weight ratio of thiourea and thiourea derivative is out of the range, dam damage may occur during electroless tin plating.

The surfactant contributes to the improvement of appearance, denseness, smoothness, adhesion, etc. of the plated film, and various surfactants such as usual nonionic, anionic, cationic or amphoteric surfactants can be used. Examples of the nonionic surfactant include C ₁ to C ₂₀ alkane, C ₁ to C ₂₀ alkanol, phenol, naphthol, bisphenols, C ₁ to C ₂₅ alkylphenol, arylalkylphenol, C ₁ to C ₂₅ alkylnaphthol, C ₁ to C ₂₅ alkoxyphosphoric acid (salt), sorbitan ester, polyalkylene glycol or C ₁ to C ₂₂ aliphatic amide, and condensation reaction of about 2 to 300 moles of ethylene oxide or propylene oxide. Examples of the anionic surfactant include alkylsulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, alkylbenzenesulfonates, and the like. Examples of the cationic surfactant include mono to trialkylamine salts, dimethyl dialkylammonium salts, and trimethylalkylammonium salts. Examples of the amphoteric surfactant include carboxybetaine, sulfobetaine, imidazolinebetaine or amicarboxylic acid. The surfactants may be used alone or in combination of two or more. The concentration of the surfactant in the tin plating solution is not particularly limited, but is preferably about 0.01 g / L to 50 g / L.

The antioxidant is for the purpose of preventing the oxidation of Sn ^{2+ in} the plating solution, and includes an antioxidant such as hydroquinone, catechol, resorcin, proglycin, hydrazine, hypophosphorous acid, ascorbic acid, cresol sulfonic acid, phenolsulfonic acid, catechol sulfonic acid, Or a salt thereof may be used. The antioxidant may be used alone or in combination of two or more. The concentration of the antioxidant in the tin plating solution is not particularly limited, but is preferably about 0.01 g / L to 20 g / L.

According to another aspect of the present invention, in the electroless tin plating method including the step of electroless tin plating using the electroless tin plating solution, the plating temperature is suitably from 58 to 60 ° C. The plating efficiency is lowered below 58 ° C, and when the temperature exceeds 60 ° C, damage is caused to the plated body.

The composition and effect of the present invention will be described in more detail with reference to the following examples and comparative examples. However, this embodiment is intended to explain the present invention more specifically, and the scope of the present invention is not limited to these embodiments.

[Example]

Electroless tin plating solutions of Examples 1 to 8 were prepared with the components and contents shown in Table 1 below.

[Table 1] Components and content of electroless tin plating solution

[Comparative Example]

Electroless tin plating solutions of Comparative Examples 1 and 2 were prepared with the components and contents shown in Table 2 below.

[Table 2] Components and content of electroless tin plating solution

[Experimental Example]

The above Examples 1 to 8 and Comparative Examples 1 and 2 were subjected to electroless tin plating on a printed circuit board under the following conditions to measure and observe the occurrence of plating thickness, surface texture, and dam damage, Respectively. The occurrence of dam damage was confirmed at 10 points after electroless tin plating.

Plating condition: 58 占 폚 / 5 minutes

PSR Ink: PSB-4000MHF (Taiyo Ink)

Plating thickness measurement: Plating thickness meter (Roentgenanlytik MaXXi 5)

Check for surface damage and dam damage: Optical microscope (Nikon SMZ800)

[Table 3] Experimental results according to changes in content of complexing agent

From these results, it was observed that dam damage was improved and prevented according to the content of the complexing agent, and this was closely related to the thickness of the plating. Examples 1 to 8 and FIG. The plating thickness measured by electroless tin plating on the printed circuit board with the electroless tin plating solution of Comparative Examples 1 and 2 is shown.

The improvement effect means a case in which dam damage does not occur at the PSR ink interface, and it can be seen from the comparison between FIG. 2 and FIG. 3 whether there is dam damage occurring or not. In the case of FIG. 2 in which Example 6 was tested, no damages occurred due to no discoloration at the PSR ink interface. In the case of FIG. 3 in which Comparative Example 1 was tested, discoloration occurred at the PSR ink interface, This means dam damage has occurred. The improvement effect was classified into good (○), middle (△) and poor (x) depending on the degree of improvement. Dam damage was observed at 10 points after electroless tin plating. It was evaluated as good when no dam damage occurred, and it was evaluated as middle (Δ) when 4 to 6 dam damage occurred among 10 points. In all 10 points, Dam damage was evaluated as poor (x).

It is to be understood that the present invention is not limited to the above-described embodiments, but various modifications may be made by those skilled in the art without departing from the scope of the present invention.

Claims (10)

1. An electroless tin plating solution comprising a first tin (Sn ²⁺ ), an electrolyte, a complexing agent, a surfactant and an antioxidant,
Wherein the complexing agent comprises a carboxylic acid, thiourea and thiourea derivative
Electroless tin plating solution.
The method according to claim 1,
The electroless the stannous ^{(Sn 2+) 7 ~ 15g /} L, the electrolyte 40 ~ 200g / L, the complexing agent is thiourea, based on the tin plating the entire 1L: the weight ratio of the thiourea derivative 5-7: 3 to 5 and a total content of 50 to 800 g / L, 0.01 to 50 g / L of said surfactant and 0.01 to 20 g / L of said antioxidant
Electroless tin plating solution.
The method according to claim 1,
^Wherein the source of the first tin (Sn ²⁺ ) is at least one selected from the group consisting of tin methanesulfonate, tin sulfate, tin sulfamate and tin pyrophosphate.
Electroless tin plating solution.
The method according to claim 1,
Wherein the electrolyte is at least one selected from the group consisting of methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid and 1-butanesulfonic acid as the alkanesulfonic acid
Electroless tin plating solution.
The method according to claim 1,
The carboxylic acid of the complexing agent is at least one selected from the group consisting of oxycarboxylic acid, polycarboxylic acid, monocarboxylic acid, and salts thereof,
The thiourea derivative of the complexing agent may be at least one selected from the group consisting of 1,3-dimethyl thiourea, trimethyl thiourea, diethyl thiourea, N, N-diisopropyl thiourea, allyl thiourea, acetyl thiourea, 3-diphenyl thiourea, and thiourea dioxide.
Electroless tin plating solution.
6. The method of claim 5,
The carboxylic acid of the complexing agent is selected from the group consisting of gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptolactone, formic acid, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid, malonic acid, malic acid, tartaric acid, diglycolic acid, And a salt thereof.
Electroless tin plating solution.
The method according to claim 1,
Wherein the surfactant is at least one selected from the group consisting of nonionic, anionic, cationic and amphoteric surfactants
Electroless tin plating solution.
8. The method of claim 7,
The nonionic surfactant is selected from the group consisting of C ₁ to C ₂₀ alkane, C ₁ to C ₂₀ alkanol, phenol, naphthol, bisphenols, C ₁ to C ₂₅ alkylphenol, arylalkylphenol, C ₁ to C ₂₅ alkylnaphthol, At least one selected from the group consisting of C ₂ to C ₂₅ alkoxyphosphoric acid (salts), sorbitan esters, polyalkylene glycols, or C ₁ to C ₂₂ aliphatic amide condensed with about 2 to 300 moles of ethylene oxide or propylene oxide .
Wherein the anionic surfactant is at least one selected from the group consisting of alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates and alkylbenzenesulfonates,
Wherein the cationic surfactant is at least one selected from the group consisting of mono to trialkylamine salts, dimethyl dialkyl ammonium salts and trimethyl alkyl ammonium salts,
Wherein the amphoteric surfactant is at least one selected from the group consisting of carboxybetaine, sulfobetaine, imidazoline betaine and amicarboxylic acid
Electroless tin plating solution.
The method according to claim 1,
Wherein the antioxidant is at least one selected from the group consisting of hydroquinone, catechol, resorcin, proroglucine, hydrazine, hypophosphorous acid, ascorbic acid, cresol sulfonic acid, phenolsulfonic acid, catechol sulfonic acid, hydroquinone sulfonic acid, Characterized by
Electroless tin plating solution.
10. A method for manufacturing a tin plating bath, comprising the steps of electroless tin plating using the electroless tin plating solution according to any one of claims 1 to 9
Electroless tin plating method.

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