KR20190091142A - Electrolyte composition for tin plating using ionic liquid prepared by mixing choline chloride and thiourea and plating method using the same - Google Patents

Abstract

The present invention relates to an electrolyte composition for tin plating using an ionic liquid prepared by mixing choline chloride and thiourea and a plating method using the same and, more specifically, relates to an electrolyte composition of ionic liquid used as a reduced electroless tin plating solution, wherein an ionic liquid is mixed at an optimum ratio, and malonic acid, oxalic acid, or ethylene glycol is added. Moreover, an additive such as dimethylthiourea, titanium chloride or sodium phosphate as a reducing agent, and water is added as a complexing agent derivative to provide low viscosity and high ionic conductivity. Therefore, metal can be quickly and stably extracted, and a film can be quickly and thickly grown.

Description

Electrolytic composition for tin plating using ionic liquid prepared by mixing choline chloride and thiourea and plating method using the same}

The present invention relates to an ionic liquid electrolyte composition and a method for preparing the same. More specifically, the ionic liquid is mixed at an optimum blending ratio to prepare a low crystallization temperature, a viscosity, and a high ion conductivity, and a complexing agent and a derivative. The present invention provides a composition of an ionic liquid electrolyte applicable to electroless tin plating by adding an additive such as a reducing agent and a manufacturing method thereof.

Traditionally, the use of methanesulfonic acid baths (Metal Finishing, January, AESF, p17 (1990)) to protect the environment has been tested and practically used in some lines worldwide.

Methane sulfonic acid removes hydrochloric acid through a purification process. However, commercially available methanesulfonic acid does not completely remove hydrochloric acid and remains at several to several tens of ppm levels. The remaining hydrochloric acid lowers the plating efficiency in the actual plating process of the mass production site, adversely affects the plating film, and eventually increases the defective rate. In addition, sulfur compounds which are incidental to the synthesis of methanesulfonic acid also affect the plating properties, and it is difficult to treat the wastewater with remaining hydrochloric acid and sulfur compounds.

Alkanesulfonic acids such as methanesulfonic acid, ethanesulfonic acid and propanesulfonic acid; Alkanolsulfonic acids such as 2-hydroxyethanesulfonic acid and 2-hydroxypropanesulfonic acid; Tin plating baths or tin alloy plating baths containing organic sulfonic acids such as aromatic sulfonic acids such as p-phenolsulfonic acid as base acids have been widely used since they are easy to drain and have excellent solubility of tin salts. 10-1574229, and Republic of Korea Patent No. 10-1608073).

In such tin plating baths and tin alloy plating baths based on aliphatic sulfonic acids such as organic sulfonic acids, in particular, alkanesulfonic acids, which are widely used, there is a relation between the purity of aliphatic sulfonic acids and the properties of the resulting plating film, and the purity of aliphatic sulfonic acids. If low and a small amount of impurities are contained, a problem arises that adversely affects the properties of the plated film.

The general characteristics of ionic liquids are organic cations and organic / inorganic anions, which do not form crystals due to asymmetry in size, and the lattice energy of the crystal structure is reduced. Refers to the substance present. Ionic liquids have low vapor pressure, non-flammability, high-density ion movement, high ion conductivity, and electrochemically stable characteristics.

In addition, ionic liquids are called future clean organic solvents and electrolytes. Recently, ionic liquids are used in various fields such as fuel cells and solar cells as electrolytes, electrochemicals, and separation processes. Are activated (Korean Patent No. 10-1630210, Korean Patent No. 10-1473039, and Korean Patent No. 10-1488781).

Although some patents are filed in Korea, commercialization using them is insignificant, and the majority of products using ionic liquids are supplied from overseas by some companies in Korea.

For electronic parts and automotive electronic parts, it is necessary to replace eco-friendly materials due to Pb environmental harmfulness, and tin is a representative material that has the most interest. Electroless tin plating, a surface treatment most commonly used in the industry, is applied to many industries such as semiconductor packaging, printed circuit boards and plating of various electronic components. In the case of substitution type electroless tin plating, although the plating speed is fast, there is a limitation that the plating thickness cannot be increased by a certain thickness or more.

Accordingly, the present inventors have made efforts to improve the problems of the electroless tin plating electrolytes conventionally used as described above, and as a result, the ionic liquids are mixed at an optimum blending ratio, and additives such as complexing papers, derivatives, and reducing agents are added. Manufactured to have low crystallization temperature, viscosity and high ionic conductivity, it enables fast and stable metal precipitation reaction, so that the plating solution is stable and the film such as tin or aluminum can be grown quickly and thickly at room temperature on copper or copper alloy. By confirming that the present invention was completed, the present invention was completed.

It is an object of the present invention to mix ionic liquids in an optimum blending ratio and to add additives such as complexing agents, derivatives, reducing agents and the like to significantly lower crystallization temperatures and lower viscosities compared to any ionic liquid or ionic liquid and additive composition. And compositions of ionic liquid electrolytes applicable to electroless tin plating, which are prepared to have high ionic conductivity, and methods of making the same.

In order to achieve the above object, the present invention

Choline chloride;

Thiourea;

Any one or two or more additives selected from the group consisting of malonic acid, ethylene glycol, ethylene alcohol, propylene glycol, propylene alcohol, succinic acid, oxalic acid and citric acid; And

Any one or two or more selected from the group consisting of a complexing agent derivative, a reducing agent and water;

It provides an ionic liquid electrolyte composition for electroless tin plating comprising a.

In addition,

i) mixing Choline chloride and Thiourea;

ii) adding one or more selected from the group consisting of malonic acid, ethylene glycol, ethylene alcohol, propylene glycol, propylene alcohol, succinic acid, oxalic acid and citric acid; And

iii) adding any one or two or more selected from the group consisting of complexing agent derivatives, reducing agents and water;

It provides, a method for producing an ionic liquid electrolyte composition for electroless tin plating.

In addition, the present invention is an ionic liquid electrolyte composition for electroless tin plating according to the present invention; And a water-soluble tin; provides an electroless tin plating solution comprising a.

In addition, the present invention provides an electroless tin plating method comprising treating the electroless tin plating solution according to the present invention to copper or a copper alloy.

The method for preparing an electrolyte for electroless tin plating using an ionic liquid according to the present invention is environmentally friendly by using choline chloride and thiourea, and an electrolyte having low viscosity and high ionic conductivity may be prepared according to a mixing ratio. In addition, ethylene glycol or the like is added to enable a fast and stable metal precipitation reaction, and thus the plating solution is stable. Even in electronic parts, a reduced type electroless to grow a thick or thick film such as tin or aluminum on a copper or copper alloy. It can be used as a solution solution.

In addition, the method for preparing an electrolyte using an ionic liquid according to the present invention can prepare an ionic liquid electrolyte having high ionic conductivity and low crystallization temperature by adding additives such as dimethylthiourea, malonic acid, sodium phosphate, and water. have. By using this, it can be used as a reducing type electroless plating solution that can grow a plating film quickly and thickly even at room temperature, and can be applied to semiconductor packaging, printed circuit board, and various electronic component fields.

1 is a graph showing viscosity and ionic conductivity with temperature by addition of malonic acid as an additive to a mixture of choline chloride and thiourea.
2 is a graph showing viscosity and ionic conductivity with temperature by adding oxalic acid as an additive to a mixture of choline chloride and thiourea.
3 is a graph showing viscosity and ionic conductivity with temperature by adding ethylene glycol as an additive to a mixture of choline chloride and thiourea.

Hereinafter, the present invention will be described in detail.

The present invention

Choline chloride;

Thiourea;

Any one or two or more additives selected from the group consisting of malonic acid, ethylene glycol, ethylene alcohol, propylene glycol, propylene alcohol, succinic acid, oxalic acid and citric acid; And

Any one or two or more selected from the group consisting of a complexing agent derivative, a reducing agent and water;

It provides an ionic liquid electrolyte composition for electroless tin plating comprising a.

In the composition, choline chloride and thiourea are preferably mixed in a ratio of 1.2: 1 to 1: 1.5 mol, and more preferably in a ratio of 1: 1 mol.

In the composition, it is preferable to use malonic acid, ethylene glycol or oxalic acid as the additive. The additive, such as malonic acid, ethylene glycol or oxalic acid, is preferably mixed with any one of choline chloride or thiourea in an amount of 1: 0.1 to 0.5 mol (mol), and choline chloride, thiourea and additives are 1: 1. More preferably, it is mixed in a ratio of 0.1 to 0.5 mol.

The complexing agent derivative is preferably dimethylthiourea, and the reducing agent is preferably any one or two or more of titanium chloride or sodium phosphate.

The complexing agent derivative and additives such as malonic acid, ethylene glycol or oxalic acid are preferably in a ratio of 0.7 to 2: 1, and the additives such as reducing agent and malonic acid, ethylene glycol or oxalic acid are in a concentration of 0.5 to 0.2: 1. But is not limited thereto.

The water is preferably added 1 to 6 wt% of the total composition, and more preferably 5 to 6 wt%, but is not limited thereto.

In addition,

i) mixing Choline chloride and Thiourea;

ii) adding one or more selected from the group consisting of malonic acid, ethylene glycol, ethylene alcohol, propylene glycol, propylene alcohol, succinic acid, oxalic acid and citric acid; And

iii) adding any one or two or more selected from the group consisting of complexing agent derivatives, reducing agents and water;

It provides, a method for producing an ionic liquid electrolyte composition for electroless tin plating.

In the above production method, the choline chloride and the thiourea in step i) is preferably mixed in a ratio of 1.2: 1 to 1: 1.5 mol (mol), more preferably in a 1: 1 mol (mol) ratio.

In the above production method, the additive in step ii) is preferably used malonic acid, ethylene glycol or oxalic acid. The additive, such as malonic acid, ethylene glycol or oxalic acid, is preferably mixed with any one of choline chloride or thiourea in an amount of 1: 0.1 to 0.5 mol (mol), and choline chloride, thiourea and additives are 1: 1. More preferably, it is mixed in a ratio of 0.1 to 0.5 mol.

In the above production method, the complexing agent derivative in step iii) is preferably dimethylthiourea, and the reducing agent is preferably any one or two or more of titanium chloride or sodium phosphate.

In addition, the present invention is an ionic liquid electrolyte composition for electroless tin plating according to the present invention; And a water-soluble tin; provides an electroless tin plating solution comprising a.

The electroless tin plating solution may further include a complexing agent, a surfactant, or an antioxidant.

The said surfactant contributes to improvement of the appearance, compactness, smoothness, adhesiveness, etc. of a plating film, and various surfactants, such as a normal nonionic, anionic, cationic, or amphoteric, can be used. Surfactant can be used individually by 1 type or in mixture of 2 or more types. The concentration of the surfactant in the electroless plating solution is not particularly limited, but is preferably about 0.01 g / L to 50 g / L.

The antioxidant is intended to prevent oxidation of tin and the like in the electroless plating solution. Hydroquinone sulfonic acid, salts thereof, and the like can be used. Antioxidant can be used individually by 1 type or in mixture of 2 or more types. The concentration of the antioxidant in the electroless plating solution is not particularly limited, but is usually about 0.01 g / L to 20 g / L.

In addition, the present invention provides an electroless tin plating method using the electroless tin plating solution according to the present invention.

The electroless plating method may include treating the copper or copper alloy with an electroless tin plating solution including an ionic liquid electrolyte composition.

Hereinafter, the present invention will be described in detail with reference to Examples.

The invention may be better understood by the following examples, which are intended for purposes of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

< Example  1>

Choline chloride and Thiourea were mixed to prepare a deep eutectic solvent (DES). The molar ratio of thiourea was carried out up to 30 to 80 mol%, and the crystallization temperature (freezing point) was measured by lowering the temperature after completely dissolving choline chloride and thiourea.

In the crystallization temperature measurement method, the solution was placed in a double beaker as a magnetic plate, placed in a chiller (low temperature circulation tank), and the temperature was lowered. The crystallization temperature was measured by visually confirming the temperature at which the transparent solution became cloudy.

The results are shown in Table 1 below. The lowest crystallization temperature was measured at 25 ° C. when the thiourea was 50 mol%.

Crystallization temperature according to mole percent of choline chloride and thiourea Choline chloride (mol%) Thiourea (mol%) Crystallization temperature (℃) 100 0 302 70 30 124 65 35 110 60 40 60 55 45 42 50 50 25 45 55 32 40 60 38 35 65 62 30 70 70 25 75 84 20 80 112 0 100 182

< Example  2>

After mixing 1 mol of choline chloride and 1 mol of thiourea, an ionic liquid was prepared by adding 0.5 mol of an additive, and then dissolved and lowered to determine the crystallization temperature (freezing point).

Crystallization temperature was measured in the same manner as in <Example 1>.

The results are shown in Table 2 below. Ethylene alcohol, propylene glycol, propyl alcohol and succinic acid showed little difference in crystallization temperature. The crystallization temperature of ethylene glycol decreased to 10 ° C, malonic acid to 12 ° C, and oxalic acid to 13 ° C.

Crystallization Temperature According to Additive Type additive Crystallization temperature (℃) None additives 25 Ethylene glycol
(Ethylene glycol) 10 Ethylene alcohol
(Ethylene alcohol) 22 Propylene glycol
(propylene glycol) 23 Profile alcohol
(propyl alcohol) 25 Malonic acid
(malonic acid) 12 Succinic acid
(succinic acid) 20 Oxalic acid
(oxalic acid) 13

< Example  3>

1 mol of choline chloride and 1 mol of thiourea were mixed to prepare an ionic liquid, and then 0.5 mol of malonic acid, ethylene glycol, and oxalic acid were added, respectively, to measure viscosity and conductivity.

The viscosity measurement method was measured using DV2T (digital viscometer). The solvent was prepared in a 300 ml beaker, and the speed was adjusted to maintain 90% to 100% of% Torque by using a No. 2 spindle to measure the viscosity according to temperature.

The ion conductivity measurement method was measured using Multi-Range Conductivity Meters. The prepared solvent was placed in a 300 ml beaker, and ionic conductivity was measured according to temperature.

The results are shown in Tables 3 to 5, and FIGS. 1 to 3.

Viscosity and Ionic Conductivity with Malonic Acid Addition Choline Chloride (1 mol) + Thiourea (1 mol)
+ Malonic acid (0.5 mol) Viscosity (cp) Ion Conductivity (㎲ / cm) 70 ℃ 203 1715 60 ℃ 230 1618 50 ℃ 254 1459 45 ℃ 278 1295 40 ℃ 301 1122 35 ℃ 399 1005 30 ℃ 513 857 25 ℃ 634 754 20 ℃ 789 641 15 ℃ 1247 600 10 ℃ 1621 556

Viscosity and Ionic Conductivity with Addition of Oxalic Acid Choline Chloride (1 mol) + Thiourea (1 mol)
+ Malonic acid (0.5 mol) Viscosity (cp) Ion Conductivity (㎲ / cm) 70 ℃ 277 1107 60 ℃ 291 1031 50 ℃ 369 968 45 ℃ 447 886 40 ℃ 522 723 35 ℃ 726 699 30 ℃ 1011 634 25 ℃ 1191 587 20 ℃ 1631 536 15 ℃ 1801 - 10 ℃ - -

Viscosity and Ion Conductivity with Addition of Ethylene Glycol Choline Chloride (1 mol) + Thiourea (1 mol)
+ Ethylene glycol (0.5 mol) Viscosity (cp) Ion Conductivity (㎲ / cm) 70 ℃ 181 1910 60 ℃ 186 1813 50 ℃ 195 1687 45 ℃ 216 1586 40 ℃ 234 1349 35 ℃ 285 1239 30 ℃ 348 1130 25 ℃ 500 975 20 ℃ 684 891 15 ℃ 838 747 10 ℃ - -

< Example  4>

After mixing 1 mol of choline chloride and 1 mol of thiourea, an ionic liquid is prepared, and either malonic acid, oxalic acid or ethylene glycol is added as an additive, and dimethylthiourea as a complexing agent derivative, titanium chloride or phosphoric acid as a reducing agent. Electrolytic tin plating was performed by adding either sodium and water.

Preparation of Electroless Tin Plating Electrolyte Example 4-1 Example 4-2 Example 4-3 Example 4-4 Example 4-5 Example 4-6 Tin chloride 12 g / L 12 g / L 12 g / L 12 g / L 12 g / L 12 g / L Malonic acid 52 g / L 52 g / L 52 g / L 52 g / L Oxalic acid 45 g / L Ethylene
Glycol 22.83 ml / L Dimethylthio
Element 40 g / L 40 g / L 40 g / L Titanium chloride 2.92 mL / L 2.92 mL / L 2.92 mL / L Sodium phosphate 1.369 g / L 1.369 g / L 1.369 g / L water 1 wt% 3 wt%

Preparation of Electroless Tin Plating Electrolyte Example 4-7 Example 4-8 Example 4-9 Example 4-10 Example 4-11 Tin chloride 12 g / L 12 g / L 12 g / L 12 g / L 12 g / L Malonic acid 52 g / L 52 g / L 52 g / L 52 g / L 52 g / L Oxalic acid Ethylene
Glycol Dimethylthio
Element 40 g / L 40 g / L 40 g / L 40 g / L 40 g / L Titanium chloride 2.92 mL / L Sodium phosphate 1.369 g / L 1.369 g / L 1.369 g / L 1.369 g / L water 6 wt% 1 wt% 3 wt% 6 wt%

Preparation of Electroless Tin Plating Electrolyte Comparative Example 4-1 Comparative Example 4-2 Comparative Example 4-3 Tin chloride 12 g / L 12 g / L 12 g / L Malonic acid 52 g / L Oxalic acid 45 g / L Ethylene
Glycol 22.83 ml / L Dimethylthio
Element Titanium chloride 2.92 mL / L 2.92 mL / L 2.92 mL / L Sodium phosphate water

In the electroless tin plating method, tin chloride was first added to an ionic liquid as a metal salt, and an electroless tin plating electrolyte was prepared using the additive. Then, the Hull Cell Test (Hull Cell Test) was used, and the copper plate was degreased, washed with water, and etched, and electroless tin plated at 70 ° C. for 10 minutes. Plating thickness was measured using a plating thickness meter (XRF; 150WT, ISP, Korea). From this result, the thickness of the electroless tin plating according to the content of the additive, the complexing agent derivative, the reducing agent and the water could be measured.

Electroless Tin Plating Thickness According to Complexing Derivative, Reducing Agent and Water Content Surface texture Plating thickness ( μm ) Example 4-1 Good 0.42 Example 4-2 Good 0.14 Example 4-3 Good 0.17 Example 4-4 Good 0.55 Example 4-5 Good 0.85 Example 4-6 Good 0.99 Example 4-7 Good 1.36 Example 4-8 Good 0.42 Example 4-9 Good 1.01 Example 4-10 Good 1.23 Example 4-11 Good 1.51 Comparative Example 4-1 Good 0.30 Comparative Example 4-2 Good 0.10 Comparative Example 4-3 Good 0.14

The result was that the plating thickness when the ignition was added dimethyl thiourea as the derivative increases, which, because not become a Cu and Sn ^{2 +} reaction, dimethylthiotoluene to lower the equilibrium potential of the Cu (equilibrium electrode potential) than Sn It is because a complexing agent derivative such as urea is added, and it becomes Cu (Tu) ₄ ⁺ , which is a complex with copper, and dissolves at a lower potential, and tin ions are reduced to vacancy, thereby causing a displacement reaction.

In addition, when the sodium chloride (Sodium phosphate) and titanium chloride (Titanium chloride) is added as a reducing agent, the plating thickness is increased, and the plating efficiency was higher when sodium chloride was added than titanium chloride.

In addition, the plating efficiency was increased by the addition of water, and it was confirmed that plating was possible up to 1.51 μm when 6 wt% was added.

Claims (9)

Choline chloride;
Thiourea;
Any one or two or more additives selected from the group consisting of malonic acid, ethylene glycol, ethylene alcohol, propylene glycol, propylene alcohol, succinic acid, oxalic acid and citric acid; And
Any one or two or more selected from the group consisting of a complexing agent derivative, a reducing agent and water;
Ionic liquid electrolyte composition for electroless tin plating comprising a.
The method of claim 1,
The choline chloride and thiourea is ionic liquid electrolyte composition for electroless tin plating, characterized in that mixed in a 1: 1 mol (mol) ratio.
The method of claim 1,
The choline chloride, thiourea and additives are ionic liquid electrolyte composition for electroless tin plating, characterized in that the mixture is 1: 1 to 0.1 to 0.5 mol (mol) ratio.
The method of claim 1,
The complexing agent derivative is an ionic liquid electrolyte composition for electroless tin plating, characterized in that dimethylthiourea.
The method of claim 1,
The reducing agent is titanium chloride or sodium phosphate ionic liquid electrolyte composition for electroless tin plating, characterized in that.
The method of claim 1,
The water is an ionic liquid electrolyte composition for electroless tin plating, characterized in that 1 to 6 wt% of the total composition land.
i) mixing Choline chloride and Thiourea;
ii) adding one or more selected from the group consisting of malonic acid, ethylene glycol, ethylene alcohol, propylene glycol, propylene alcohol, succinic acid, oxalic acid and citric acid; And
iii) adding any one or two or more selected from the group consisting of complexing agent derivatives, reducing agents and water;
Method for producing an ionic liquid electrolyte composition for electroless tin plating, comprising a.
An ionic liquid electrolyte composition for electroless tin plating according to any one of claims 1 to 6; And a water soluble tin.
An electroless tin plating method comprising the step of treating the electroless tin plating liquid of claim 8 to copper or a copper alloy.

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