KR101840435B1 - Tin electroplating solution and plating method using the same - Google Patents

Abstract

Disclosed are a tin electroplating solution which can reduce an illuminance value of a plating film when plating an electronic component, and an electroplating method using the same. According to an embodiment of the present invention, the tin electroplating solution comprises: a tin salt providing a divalent tin ion; an electrolyte; a pH adjusting agent; a surfactant; a complexing agent; and an auxiliary complexing agent. As the complexing agent uses two or more compounds by including tartaric acid, the tartaric acid is included as much as the amount of 100-200 g per 1 L of the tin electroplating solution. In addition, the auxiliary complexing agent uses an ethoxylate system, and is included as much as the amount of 5-15g per 1 L of the tin electroplating solution.

Description

TECHNICAL FIELD [0001] The present invention relates to a tin electroplating solution and a plating method using the tin electroplating solution.

More particularly, the present invention relates to a tin electroplating solution and a plating method using the tin electroplating solution.

Recent advances in intelligent telecommunication (IT) technology have led to rapid progress in the weight reduction, miniaturization and high performance of electronic devices such as smart phones, smart pads, notebook personal computers and the like . This process is performed through miniaturization, weight reduction, thinning, and high functioning of the electronic components constituting these electronic devices, and ultimately it is required to support a high reliability improvement of the electronic components.

One factor that affects the reliability of electronic components is the electrical connection between the electronic components. Generally, electroplating is performed for electrical connection between electronic components. Electroplating that has excellent electrical characteristics and can ensure reliability for a long time is required. Conventionally, a lot of tin-lead alloy solder has been used for plating electronic components. However, there is a tendency to use a plating solution which does not contain lead in recent years due to the harmfulness to the human body and environmental pollution. As a reflection of this tendency, electroplating using tin plating solution is widely used. Korean Patent No. 10-1608074, "tin plating solution and plating method using the same," discloses an example of a plating solution for plating an electronic component such as a multilayer ceramic capacitor chip with tin.

BACKGROUND ART [0002] Recently, a technique for stacking a plurality of printed circuit boards (PCBs) has been widely used as one measure for miniaturization, weight reduction, thinning, and high functionality of electronic parts. A stacked PCB stacks several sheets of PCB. In this case, the top and bottom PCBs are electrically connected by forming a plating layer using electroplating. However, when plating is performed using a conventional tin plating solution at the time of PCB stacking, air bubbles and air enter between the surface curvatures of the plating layer, and the generation of via holes tends to occur.

Korean Patent No. 10-1608074, "Tin plating solution and plating method using the same,

One of the problems to be solved by the present invention is to provide a tin electroplating solution and a plating method using the tin electroplating solution which can lower the roughness value of the plating film when plating electronic components.

Another object of the present invention is to provide a tin electroplating solution and a plating method using the tin electroplating solution that can prevent discoloration and deformation of a solder resistor (SR) on a PCB substrate on which electronic components are mounted.

Another object of the present invention is to provide a tin electroplating solution capable of preventing the occurrence of via holes between the plating layers when a PCB is plated to produce electronic parts by stacking a plurality of PCBs, Thereby providing a plating method.

According to an aspect of the present invention, there is provided a tin electroplating solution comprising a tin salt, an electrolyte, a pH adjuster, a surfactant, a complexing agent, and a secondary complexing agent to provide divalent tin ions. The complexing agent includes tartaric acid, and at least two compounds are used. The tartaric acid includes 100 g to 200 g based on 1 L of the tin electroplating solution. An ethoxylate system is used as the auxiliary complexing agent, and the amount of the auxiliary complexing agent is 5 g to 15 g per 1 L of the tin electroplating solution.

According to an aspect of the embodiment, the tin salt may be one or more selected from the group consisting of tin methanesulfonate, tin sulfate, tin sulfamate, and tin pyrophosphate.

According to another aspect of this embodiment, the tin salt may comprise 15 g to 25 g of the divalent tin ion for 1 liter of the tin electroplating solution.

According to another aspect of the above embodiment, the electrolyte may be alkanesulfonic acid.

According to another aspect of the embodiment, the pH adjuster may be adjusted so as to maintain the pH of the tin electroplating solution in the range of 2 to 5.

According to another aspect of the embodiment, the surfactant may be contained in an amount of 0.01 g to 50 g per liter of the tin electroplating solution.

According to another aspect of the present invention, the complexing agent may be at least one selected from the group consisting of gluconic acid, glucoheptonic acid, gluconolactone, glucoheptolactone, formic acid, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid, malonic acid, , Citric acid, polyglycolic acid, and salts thereof.

According to another aspect of the embodiment, the complexing agent may be contained in an amount of 100 g to 300 g or less with respect to 1 L of the tin electroplating solution.

According to an embodiment of the present invention, there is provided a method of plating a tin electroplating solution according to an embodiment of the present invention, comprising: preparing a tin electroplating solution according to an embodiment of the present invention; Thereby forming a tin plating layer.

If the electronic component is plated using the tin electroplating solution according to one embodiment of the present invention, the illuminance value of the surface of the plating can be lowered. As the roughness value of the plating surface is lower, the occurrence of via holes can be prevented or prevented from occurring when the PCB is laminated after plating, so that not only the productivity but also the defect rate can be reduced in the manufacturing process of the electronic component. In addition, since discoloration and deformation of the solder resistors SR in the PCB can be prevented, not only the electrical connection of the electronic parts is excellent but also the reliability can be improved.

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.

FIGS. 1A to 1D are photographs of a surface of a plated sample using a tin electroplating solution of Examples 1 to 4, respectively, by a scanning electron microscope.
1E to 1G are photographs of a surface of a plated sample using a tin electroplating solution of Comparative Examples 1 to 3, respectively, by a scanning electron microscope.
FIGS. 2A to 2D are photographs of the surface of the plated specimen using the tin electroplating solutions of Examples 1 to 4, respectively, taken by an optical microscope.
Figs. 2E to 2G are photographs of the surface of the plated specimen using the tin electroplating solutions of Comparative Examples 1 to 3, respectively, taken by an optical microscope. Fig.
2H is a photograph of the surface of the specimen before plating is photographed with an optical microscope.
FIGS. 3A to 3C are photographs of a surface of a specimen plated using the tin electroplating solutions of Examples 5 to 7, respectively, by scanning electron microscopy. FIG.
FIGS. 3D to 3E are photographs of the surface of a plated sample using a tin electroplating solution of Comparative Example 4 and Comparative Example 5, respectively, by a scanning electron microscope.
4A to 4C are photographs of the surface of a plated sample using the tin electroplating solutions of Examples 5 to 7, respectively, taken by an optical microscope.
Figs. 4D and 4E are photographs of the surface of the plated specimen using the tin electroplating solution of Comparative Example 4 and Comparative Example 5, respectively, taken by an optical microscope. Fig.
FIG. 4F is a photograph of the surface of the specimen before plating, taken by an optical microscope.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The terms and words used in the present specification are selected in consideration of the functions in the embodiments, and the meaning of the terms may vary depending on the intention or custom of the invention. Therefore, the terms used in the following embodiments are defined according to their definitions when they are specifically defined in this specification, and unless otherwise specified, they should be construed in a sense generally recognized by those skilled in the art. And 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 tin electroplating solution according to an embodiment of the present invention includes a tin salt, an electrolyte, a pH adjuster, a surfactant, a complexing agent, and a secondary complexing agent to provide divalent tin ions. Here, at least two compounds which necessarily contain tartaric acid are used as the complexing agent. Since the tin electroplating solution contains at least two kinds of complexing agents and auxiliary complexing agents necessarily containing tartaric acid, the illuminance value of the plating layer is lowered, and as a result, a via hole is generated in the lamination of the printed circuit board (PCB) It is possible to achieve an effect of improving the productivity of the electronic component manufacturing process and lowering the defect rate.

Tin salts are a source of divalent tin ions in the tin electroplating solution and are soluble in water. According to one aspect of the embodiment, the tin salt is preferably one or more selected from the group consisting of tin methanesulfonate, tin sulfate, tin sulfamate and tin pyrophosphate. And the tin salt preferably contains 50 g to 90 g of divalent tin ions per liter of the tin electroplating solution. If the amount of divalent tin ions is less than 50 g per 1 L of the tin electroplating solution, the plating rate is lowered to not satisfy the industrially required productivity, and the smoothness and film uniformity of the tin plating layer may be impaired. On the other hand, when the divalent tin ion exceeds 90 g with respect to 1 L of the tin electroplating solution, the amount of divalent tin ions in the plating solution increases, so that precipitation formation of the tin product can not be avoided. In order to produce industrially, it is usual that there is a certain level fluctuation depending on the plating condition when tin salt is used, and it is possible to form a tin plating layer of more stable quality considering unavoidable fluctuation which can not be managed by the plating condition Because.

Electrolyte refers to a substance that when dissolved in a particular solvent, becomes conductive. According to an aspect of the embodiment, an alkanesulfonic acid electrolyte may be used as the electrolyte. Specific examples thereof include methanesulfonic acid, ethanesulfonic acid, 1-propylsulfonic acid, 2-propylsulfonic acid, and pentanesulfonic acid. At this time, the alkanesulfonic acid electrolyte may be used singly or in combination of two or more, methanesulfonic acid being preferred. The electrolyte is preferably 20 g to 500 g, more preferably 60 g to 300 g, per 1 L of the tin electroplating solution. When the content of the electrolyte is less than 20 g or more than 500 g, not only the thickness of the plating layer or the plating film in the tin plating process may be reduced, but also the uniformity may be deteriorated.

The pH adjuster is for fine adjustment of the pH of the tin plating solution. According to one aspect of the embodiment, the pH adjuster is preferably adjusted so that the pH of the tin electroplating solution is maintained in the range of 2 to 5. If the pH of the tin electroplating solution is less than 2, the plating efficiency increases but it may cause safety problems in production. If the pH exceeds 5, the plating efficiency decreases. The pH adjusting agent may be an alkaline pH adjusting agent or an acidic pH adjusting agent. As the alkaline pH adjusting agent, sodium hydroxide, potassium hydroxide, ammonia water, etc. may be used. One of them may be used singly or two or more of them may be used in combination. In order to have a preferable pH range of the tin electroplating solution, 10 g to 300 g may be added. Examples of the acidic pH adjusting agent include methanesulfonic acid, ethanesulfonic acid, sulfuric acid, isethionic acid, and the like. One of them may be used singly or a mixture of two or more thereof may be used. The pH of the tin electroplating solution may be adjusted It may be added in an amount of 20 to 150 g per 1 L of the tin electroplating solution. The alkaline pH adjusting agent and the acidic pH adjusting agent can be appropriately adjusted according to the content of the added substance.

The surfactant contributes to the improvement of appearance, compactness, smoothness and adhesion of the plated film. According to one aspect of the embodiment, the nonionic surfactant, the anionic surfactant, the cationic surfactant, the amphoteric surfactant and the like can be used as the surfactant. The nonionic surfactants include ethylene oxide and propylene oxide such as alkanol, phenol, naphthol, bisphenols, alkylphenol, arylalkylphenol, alkylnaphthol, alkoxyphosphoric acid (salt), sorbitan ester, polyalkylene glycol, And 2 to 300 moles of the condensation product may be used. As the anionic surfactant, alkyl sulfate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether sulfate, alkylbenzenesulfonate and the like can be used. As the cationic surfactant, mono to trialkylamine salts, dimethyl dialkylammonium salts, trimethylalkylammonium salts and the like can be used. The amphoteric surfactant may be carboxybetaine, sulfobetaine, imidazolinebetaine, amicarboxylic acid, and the like. The surfactants may be used alone or in combination of two or more. The content of the surfactant in the tin electroplating solution is not particularly limited, but is preferably 0.01 g to 50 g per 1 L of the tin electroplating solution.

The complexing agent forms a complex with tin ions. Examples of the complexing agent include oxycarboxylic acid, polycarboxylic acid, monocarboxylic acid and salts thereof. Specifically, 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 salts thereof. The selection of the type and amount of the complexing agent is important in terms of stability of the plating solution and improvement of current efficiency. According to the embodiment of the present invention, it is preferable to use two or more kinds of complexing agents which necessarily contain tartaric acid. The total content of the complexing agent containing tartaric acid is preferably 100 g to 200 g per 1 L of the tin electroplating solution. When the content of the complexing agent is less than 100 g, the plating liquid becomes unstable and a large amount of unplated is generated even if plating is performed. Further, when the content of the complexing agent exceeds 200 g, it is not dissolved well in water and causes not only sludge but also a plating rate to be lowered or a plating film structure is not formed.

The auxiliary complexing agent is a substance for preventing discoloration and deformation of SR in the PCB substrate, and may be an ethoxylate system, a carboxylate system, or the like. According to one embodiment of the present invention, an ethoxylate-based material is preferably used as the auxiliary complexing agent, and they may be used alone or in combination of two or more. Specifically, as an auxiliary complexing agent for preventing discoloration, Naphthol Ethoxylate, Ethylhexanol Ethoxylate, Thiodiglycol Ethoxylate, Sulfonated Ethoxylate, ), Sulfated alkylphenol ethoxylate, and the like can be used. Benzylpyridinium carboxylate, ethylene copolymer and the like can be used as a secondary complexing agent for preventing SR from being deformed.

In order to prevent discoloration and deformation of SR in the PCB substrate, it is preferable to use an ethoxylate system as the auxiliary complexing agent. At this time, it is preferable that the auxiliary complexing agent contains 5g to 15g per 1L of the tin electroplating solution. When the content of the auxiliary complexing agent is less than 5 g, the activation in the solution is reduced and the SR in the PCB substrate is discolored and deformed. When the content exceeds 15 g, a large amount of bubbles may be generated, .

Next, a plating method using the tin electroplating solution described above according to an embodiment of the present invention will be described. First, a tin electroplating solution is prepared according to the embodiment of the present invention described above. Then, the plating object is immersed in the prepared tin electroplating solution to form a tin plating layer.

At this time, the tin electroplating solution includes a tin salt, an electrolyte, a pH adjuster, a surfactant, a complexing agent and a sub-complexing agent which provide divalent tin ions, and at least two kinds of complexing agents necessarily containing tartaric acid are used. The auxiliary complexing agent uses an ethoxylate system. The above-described contents are overlapped with the characteristics and the content of each component constituting the tin electroplating solution, and the description of the overlapped parts is omitted. The tin electroplating solution is prepared by mixing water with an electrolyte, a complexing agent and a pH adjusting agent so that the pH value is in the range of 2 to 5, adding tin salt and stirring sufficiently. Subsequently, the tin electroplating solution can be prepared by adding the surfactant and the auxiliary complexing agent and sufficiently stirring.

Hereinafter, configurations and effects according to embodiments of the present invention will be described in detail with reference to examples and comparative examples. However, the following examples of the present invention are intended to further illustrate the present invention, and the scope of the present invention is not limited to these examples.

[First Embodiment]

The electrolytic solution, the complexing agent and the pH adjuster are mixed with water to make the pH value 2, and then the tin salt is added to the electrolytic solution to prepare a solution of 1 Lt; / RTI > Then, a surfactant, tartaric acid and gluconic acid were added as a complexing agent and stirred for 2 hours to prepare 1 L of tin electroplating solution containing the composition and content shown in the following Table 1, which were Examples 1 to 4. However, in the electro tin plating solution according to Example 1, that is, Examples 1 to 4, auxiliary complexing agent is not included in order to confirm the effect of tartaric acid as a complexing agent on the plating quality. In the contents of tin methanesulfonate, the values in parentheses indicate the content of divalent tin ions. Unless otherwise stated, known chemicals commercially available are used.

[Comparative Example 1]

Comparative Example 1 is a case where a bright tin electroplating agent (Maclee) was used. Comparative Examples 2 and 3 were prepared in the same manner as in Example 1, and 1 L of tin electroplating solution containing the components and contents shown in Table 2 below was prepared.

[Second embodiment and second comparative example]

The second example was prepared in the same manner as in the first embodiment (i.e., Examples 1 to 4) described above, except that in order to confirm the influence of the ethoxylate used as the subcomplexant on the plating quality, And 1 L of a tin electroplating solution containing the above-mentioned composition and content.

Comparative Example 4 is a case using a bright tin electroplating agent (Maclee). Comparative Example 5 was prepared in the same manner as in Example 2 except that 1 L of tin electroplating solution containing no ethoxylate was prepared as shown in Table 3 below.

[Experimental Example]

A Hull Cell copper specimen (5 cm in length, 5 cm in length) was plated at a current of 0.6 A for 12 minutes at 25 ° C. using the tin electroplating solutions of the prepared Examples 1 to 7 and Comparative Examples 1 to 5, respectively. The surfaces of the plated specimens were examined by scanning electron microscope (FE-SEM) and optical microscope, respectively.

1A to 1D are photographs of a surface of a specimen plated using the tin electroplating solutions of Examples 1 to 4 respectively by a scanning electron microscope and FIGS. 1E to 1G are photographs of Comparative Examples 1 to 3 Of the surface of the plated specimen using a tin electroplating solution. 2A to 2D are photographs of the surface of a plated sample using the tin electroplating solutions of Examples 1 to 4, respectively, and FIGS. 2E to 2G are photographs of Comparative Examples 1 to 3 Of the surface of the plated specimen using the tin electroplating solution. 2H is a photograph of the surface of the specimen before plating is photographed with an optical microscope. Table 4 below shows the roughness values (Ra) measured using the roughness measuring equipment for the surfaces of the test pieces plated with the tin electroplating solutions of Examples 1 to 4 and Comparative Examples 1 to 3. Normally, the illuminance (E) at a distance of r [m] from the point light source can be obtained by using the following equation (1).

Where F is the speed of light, A is the width of the measurement area, and I is the light intensity.

Referring to Table 4, it can be seen that in the case of Comparative Example 1, the roughness value is about 0.2, and the surface of the plating layer is considerably flat. The lower the roughness value, the less the occurrence of bubbles and the like between the plating layers during the PCB stacking, thereby minimizing the occurrence of product defects and increasing the productivity. However, Comparative Example 1 is a case of using a polishing tin electroplating solution, which contains a considerable amount of organic matter. The more the organic matter is contained, the lower the roughness value, but the organic matter causes a solder resistor attack (SR attack), causing the plating layer to collapse, misplaced plating and bonding with the side plating layer.

Therefore, in order to minimize product defects and improve productivity, a tin electroplating solution is required which has low illuminance value and can eliminate or minimize solder resistor attack. In general, the electro-tin plating solution may have an illuminance value of 0.5 to 0.6 or more, or 0.7 or more. Referring to Comparative Example 2 and Comparative Example 3 in Table 4, it can be seen that the tin electroplating solution containing no tartaric acid as a complexing agent has an illuminance value of 0.5 or more. However, referring to Examples 1 to 4 of Table 4, it can be seen that the illuminance value is lowered when tartaric acid is used as a complexing agent, and when the amount of tartaric acid is increased within a predetermined range, It can be seen that it can be lowered to 0.3 units.

FIGS. 3A to 3C are photographs of a surface of a specimen plated using the tin electroplating solutions of Examples 5 to 7 by scanning electron microscopy, and FIGS. 3 to 3E are photographs of Comparative Examples 4 and 5 Of the surface of the plated specimen using a tin electroplating solution. 4A to 4C are photographs of the surface of the plated specimen using the tin electroplating solutions of Examples 5 to 7 by an optical microscope, and FIGS. 4D and 4E are photographs of Comparative Example 4 and Comparative Example 5 Of the surface of the plated specimen using the tin electroplating solution. FIG. 4F is a photograph of the surface of the specimen before plating, taken by an optical microscope.

Referring to FIGS. 3A to 3E and 4A to 4D, when the ethoxylate is not used as the auxiliary complexing agent (Comparative Example 4 and Comparative Example 5), solder resistor attack occurs to cause surface damage, It can be seen that the solder resistor attack does not occur or is minimized when the ethoxylate is used (Examples 5 to 7).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It is possible.

Claims (9)

In the tin electroplating solution,
An electrolyte, a pH adjuster, a surfactant, a complexing agent, and a secondary complexing agent, which provide divalent tin ions,
As the complexing agent, tartaric acid is included and two or more compounds are used, and the tartaric acid includes 100 g to 200 g based on 1 L of the tin electroplating solution,
Ethoxylate system is used as the auxiliary complexing agent, and 5 to 15 g of the auxiliary plating agent is contained in 1 L of the tin electroplating solution,
The complexing agent may be at least one selected from the group consisting of gluconic acid, glucoheptonic acid, gluconolactone, glucoheptolactone, formic acid, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid, malonic acid, malic acid, A salt thereof, and a salt thereof.
The plating target of the tin electroplating solution is a PCB constituting a printed circuit board (PCB)
Wherein the tin electroplating layer formed on the PCB using the tin electroplating solution has a surface roughness of 0.322 to 0.504. The method according to claim 1,
Wherein the tin salt is at least one selected from the group consisting of tin methanesulfonate, tin sulfate, tin sulfamic acid and tin pyrophosphate. The method according to claim 1,
Wherein the tin salt comprises 15 g to 25 g of the divalent tin ions per liter of the tin electroplating solution. The method according to claim 1,
Wherein the electrolyte is an alkanesulfonic acid-based tin electroplating solution. The method according to claim 1,
Wherein the pH adjustment agent is adjusted so as to maintain the pH of the tin electroplating solution within a range of 2 to 5. The tin electroplating solution according to claim 1, The method according to claim 1,
Wherein the surfactant is contained in an amount of 0.01 g to 50 g per liter of the tin electroplating solution. delete The method according to claim 1,
Wherein the complexing agent is contained in an amount of not less than 100 g but not more than 300 g based on 1 L of the tin electroplating solution. A method for producing a tin electroplating solution, comprising: preparing a tin electroplating solution according to any one of claims 1 to 6; And
And dipping the plating object in the tin electroplating solution to form a tin plating layer.

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