JPH0742595B2 - Bright tin metal plating solution for modulated current electrolysis - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses tin-based metal plating such as tin or tin-lead alloy by using modulated current electrolytic plating such as high-speed current reversal electrolytic plating, PR electrolytic plating, and pulse electrolytic plating. The present invention relates to a tin-based metal plating solution for obtaining a bright plated film having excellent gloss ratio, reflow resistance, pinholes and other properties.

[0002]

2. Description of the Related Art In general, tin plating or tin-lead alloy plating on metal products is a surface treatment technique for facilitating soldering of electronic components.
Widely used for printed circuit boards.

Particularly, in recent years, electrical appliances have been remarkably miniaturized and their performance has been remarkably increased, and in response to this situation, the reliability has been improved by miniaturizing parts, improving corrosion resistance, and increasing the density of printed circuit boards. is there.

High-density mounting on a printed circuit board or the like is performed by resin-molding the components on the substrate, mounting the components on the front and back sides, and forming the substrate in multiple layers. Therefore, the tin plating or the tin-lead alloy plating film on the terminals or the like of the parts to be soldered to a printed circuit board or the like is required to have heat resistance capable of withstanding the heating conditions of the resin mold and maintaining the bonding characteristics. On the other hand, since the components on the printed circuit board are bonded in high density in multiple stages such as front and back, the tin plating or tin-lead alloy plating film on the component terminals must be heated many times before the actual bonding. Thermal melting and cooling and solidification are repeated, and bias tends to occur during cooling. If this film deviation occurs, the solder joint becomes defective and production efficiency is affected. Therefore, the tin-plated or tin-lead alloy plated film is required to have such a characteristic that the film is not biased even if it is heated many times, and so-called reflow resistance is a very important factor.

Further, in order to improve the reliability of the parts, it is required to eliminate pinholes and film thickness defects of the film which cause discoloration and corrosion. To this end, the crystal size of the film is made extremely small to reduce pinholes, and the plating film has a high uniform electrodeposition property with a small difference in film thickness between the current-concentrated portion and the non-concentrated portion. It is necessary to be. Furthermore, tin plating or tin lead alloy plating film,
It is required in appearance inspection that the appearance should be close to a mirror surface.

Conventionally, the tin plating or the tin-lead alloy plating film has been formed on the surface of the material to be plated by the direct current electrolytic plating method. For example, in a tin-based metal plating solution mainly composed of tin or a metal salt of tin and lead, 20 mL / L of an alkaline liquid condensate of ortho (o-) toluidine / acetaldehyde as a first brightening agent is added as a second brightening agent. As an agent
A plating film is formed by a direct current electrolysis method using a boric acid fluoride liquid plating solution added with 10 mL / L of formalin.

The film formed by this direct current electrolytic plating method has good gloss, but does not have excellent heat resistance and poor reflow resistance. That is, the heat treatment at 150 to 180 ° C. required for the resin mold for 2 to 48 hours causes a remarkable discoloration, and the solderability also deteriorates. Further, when the printed circuit board is mounted on both sides, heating at 240 ° C. for about 20 seconds is repeated three times, so that the plating film is significantly deviated and the solderability is deteriorated. For this reason, the production speed at the time of mounting is lowered, the reliability of the parts is lowered, and conduction defects and other defects are induced.

These problems are caused by changing the plating solution for direct current to, for example, a sulfamic acid solution plating solution, a sulfuric acid solution plating solution, an alkali solution plating solution, or the like, as a brightening agent, a peptide, a carboxylic acid, an aldehyde, Even if a means using a ketone system or the like is tried, it is not possible to completely solve the problem, and it is particularly difficult to solve the reflow resistance of the film and the generation of pinholes.

For this reason, it is unavoidable that the pinholes of the film are filled up by post-treatment, a dense film is formed with a very low current density, and polishing is performed by post-treatment to obtain a glossy surface. Needed. Therefore, as compared with plating on a lead frame in a reel-to-roll line, for example, the production efficiency is as low as ⅙ or less, and the manufacturing cost becomes extremely high. .

Therefore, a means for forming a tin plating or a tin-lead alloy plating film by the modulation current electroplating method, not by the conventional direct current electroplating method, has recently attracted attention. That is, high-speed current reversal electrolytic plating that reverses the polarity at a high speed of 1 Hz or more and flows a reverse current at a high frequency, PR electrolytic plating that flows a reverse current by repeating every second and minute units such as a 2-minute cathode and a 10-second anode, 10 to 1000 Hz. , Duty 40 to 75%, and the like, which is a method using pulsed electroplating or the like in which a current is interrupted at high speed. The film obtained by this modulated current electrolytic plating method has a higher production rate than that obtained by the direct current electrolytic plating method, and has a reflow resistance in the range of 1 to 15 A / dm ² .
It is excellent in many points such as heat resistance at 150 ° C and the number of pinholes.

The optimum waveform condition in the modulation current electroplating is often in the range of 100 to several 1,000 Hz, and the transistor power supply is the only power supply that satisfies this condition.
This power supply price is not only about 20 times that of the conventional one, but also the effective current capacity is about 100A. However, the production of tin and tin-lead alloy plating film generally requires at least 100 A or more, so
It is difficult to industrially utilize the waveform condition of 00 Hz or higher. However, according to the high-speed current reversal electrolytic plating method among the modulated current electrolytic plating methods, a thyristor power source can supply a power of tens of thousands of A in the range of 0.2 to 50 Hz, which is not the optimum range. , The suboptimal waveform condition area that can be industrialized can be used.

[0012]

The modulated current electrolytic plating method can obtain a high production rate as described above, but conventionally, the direct current electrolytic plating method has been used as a means for obtaining better film characteristics. The plating solution has been used as it is without changing the composition, etc., and the development has been performed only by examining the electrolytic current waveform.

However, the modulated current electrolytic plating method
When a tin plating or tin-lead alloy plating solution using a conventional DC brightener is tried, the gloss ratio of the plating film is about 1/5 as compared with the DC electrolytic plating method, and the gloss ratio of the plating film is It becomes a black region, and the gloss ratio does not improve even if it is added more. Further, the surface gloss ratio is remarkably inferior to about 60% of the film obtained by the direct current electrolytic plating method, and the appearance is in a light cloudy state, so that the appearance inspection cannot be cleared.

This is because during modulation current electroplating, a significantly thinner diffusion layer is formed as compared with the direct current electroplating method, and the luster exerting mechanism is that the reverse current and the instantaneous intermittent pulse current action work, and This is because the brightener added to the plating solution does not work effectively. That is, conventionally known brighteners, for example, ketone-based, saturated and unsaturated aldehyde-based, peptide-based, carboxylic acid-based such as crotonic acid,
Substances having a double bond between carbon and oxygen, such as ortho (o-) toluidine / acetaldehyde condensate, are extremely effective for direct current electrolytic plating, and a plating film having a specular gloss with a gloss ratio of 95% or more is obtained. However, in modulated current electroplating, the brightening agent described above has an adverse effect, causing abnormal deposition of the plating and fogging of the coating.

Further, the tin plating or the tin-lead alloy plating film by the modulation current electroplating method has a slightly better throwing power than that by the direct current electroplating method, and better characteristics are required. . Another major problem is that in the conventional DC plating solution, the brightener component is decomposed or changed by electrolysis due to a modulation current for several days. The deterioration of the brightener causes abnormal deposition of the plating, and the film obtained in this state has a surface gloss remarkably reduced to 20% or less of that obtained by the direct current electrolytic plating method, and has good reflow resistance. Range is 1
Remarkably deteriorates to 5 A / dm ² . Therefore, it is not possible to form a tin plating or tin-lead alloy plating film that maintains stable characteristics for a long period of time, and efficient production cannot be performed.

As described above, when the tin plating or the tin-lead alloy plating film is formed by the modulation current electrolytic plating method using the conventional DC plating solution, the heat resistance and the reflow resistance are higher than those by the DC electrolytic plating method. -Sexuality is improved,
This cannot maintain stable characteristics for a very long time. Also,
The desired characteristics cannot be obtained in terms of uniform electrodeposition, surface gloss, plating solution durability and reproducibility.

For this reason, there are problems such as a decrease in productivity, a poor appearance, a poor durability, a poor corrosion resistance, and an increase in manufacturing cost in high-density mounting of a plated film-formed component or a printed circuit board. Since these parts and printed circuit boards are used in many industries and fields, including computers, defects in tin plating or tin-lead alloy plating films cause computer troubles, and once they occur, they can cause a wide range of problems. It has a great impact on the reliability of the product, such as causing serious damage. Despite having such problems,
The development of a dedicated bright tin-based metal plating solution that can further improve the characteristics of the plating film formed by the modulated current electrolytic plating method has never been attempted at all.

The present invention has investigated the brighteners to be added to tin or tin-based metal plating solutions such as tin and lead, and by using the modulated current electroplating method, the problems described in the above-mentioned prior art are included. The purpose of the present invention is to provide a new bright tin-based metal plating solution that completely solves the above problem. In this specification, the definition of the term tin-based metal plating solution means the meaning of the tin plating solution and all tin alloy plating solutions.

[0019]

To achieve the above object, the present invention comprises means for adding a specific brightening agent to a tin-based metal plating solution. A specific example of the brightener is obtained by reacting 1 mol of a condensate of ortho (o-) toluidine and acetaldehyde with 0.5 to 1 mol of paraacetaldehyde in the presence of fluoroboric acid and water. Recondensation material, paraacetaldehyde 0.1
1 to 1 mol, a substance obtained by reacting 1 mol of crotonylaldehyde having an unsaturated double bond in the presence of fluoroboric acid and water, or an amine-aldehyde condensate As a brightener, a substance obtained by condensing and stabilizing paraacetaldehyde in the presence of fluoroboric acid and water, or o-phenanthroline (1,10-phenanthroline), acetoxyquinoline, ethylquinolinium salt, quinoline, A highly stable aromatic cyclic nitrogen compound consisting of one or a mixture of two or more selected from 8-hydroxyquinoline was selected as the second brightener. Then, in the tin-based metal plating solution, the first brightener alone or in combination with the second brightener,
It was added.

[0020]

The selected first and second brighteners are carbon-oxygen and carbon-oxygen-nitrogen compounds, respectively.
These are considered to be, for example, ether-bonding substances mainly due to the carbon-oxygen single bond, and thus are not decomposed by the modulated current electrolysis.

[0021]

EXAMPLES The bright tin metal plating solution for modulated current electrolysis according to the present invention will be specifically described below with reference to examples.

Example 1 The composition of the tin-based metal plating solution to which the brightening agent was added was 100 to 240 g / L of tin fluoroborate and 10 to 30 g of lead fluoroborate.
L, 80 to 130 g / L of fluoroboric acid, and 5 to 10 g / L of surfactant were used. As tin or a metal salt of tin and lead, tin sulfamate, lead sulfamate, and tin sulfate are other examples, and as free acids for pH adjustment, sulfamic acid in addition to fluoroboric acid,
Sulfuric acid or the like is used, and specific examples of the surfactant include polyoxyethylene nonylphenyl ether, polyoxyethylene derivative and the like. 1 mol of a condensate of ortho (o-) toluidine and acetaldehyde was added to 0.5 to 1 mol of paraacetaldehyde, which is a cyclic ether compound, as a brightening agent in this tin-lead alloy plating solution, and boron fluoride was added thereto. A bright tin lead alloy plating solution containing 0.35 g / L of a recondensation substance obtained by reacting in the presence of an acid and water was subjected to high-speed current reversal electrolytic plating, which is one of the modulation current electrolytic plating methods, at 18 ° C. , 12H
z, current reversal rate 1%, that is, cathode working current rate 99
%, 6 A / dm ² , the coating film plated under the conditions of sample N
o. It was set to 1.

Example 2 In the tin-lead alloy plating solution used in Example 1 above, 1 mol of crotonyl aldehyde having an unsaturated double bond was added to 0.1 to 1 mol of paraacetaldehyde as a brightener. A film obtained by plating a bright tin plating solution containing 1 mL / L of a substance obtained by reacting in the presence of boron fluoride acid and water under the same conditions as in Example 1 was used. It was set to 2.

Example 3 The tin-lead alloy plating solution used in Example 1 above was used as a first brightener with respect to 0.5 to 1 mol of paraacetaldehyde and an ortho (o
-) 1 mol of a condensate of toluidine and acetaldehyde,
0.35 g / L of recondensation substance obtained by reacting in the presence of fluoroboric acid and water, and paraacetaldehyde as a second brightening agent, condensation reaction in the presence of fluoroboric acid and water The film obtained by plating the bright tin plating solution, to which 0.1 mL / L of each of the substances obtained in this manner was added, under the same conditions as in Example 1 was used. It was set to 3.

Example 4 In the tin-lead alloy plating solution used in Example 1 above, as the first brightener, 0.1 to 1 mol of paraacetaldehyde and 1 to 1 mol of crotonyl aldehyde having an unsaturated double bond were used. 1 mL of the substance obtained by reacting a mol in the presence of boron fluoride acid and water.
/ L, paraacetaldehyde as the second brightener,
A sample obtained by plating a bright tin plating solution containing 0.5 mL / L of a substance obtained by a condensation reaction in the presence of boron fluoride acid and water under the same conditions as in Example 1 was used. It was set to 4.

Example 5 The tin-lead alloy plating solution used in Example 1 above was used as a first brightening agent with respect to 0.5 to 1 mol of paraacetaldehyde and an ortho (o
-) 1 mol of a condensate of toluidine and acetaldehyde,
0.35 g / L of a recondensation substance obtained by reacting in the presence of boron fluoride acid and water, and 0.0-phenanthroline which is an aromatic cyclic nitrogen compound as a second brightener.
06 g / L, a bright tin plating solution added respectively, was plated under the same conditions as in Example 1 to form a film.
It was set to 5.

Example 6 In the tin-lead alloy plating solution used in Example 1 above, crotonyl aldehyde 1 having an unsaturated double bond was added as a first brightener to 0.1 to 1 mol of paraacetaldehyde. 1 mL of the substance obtained by reacting a mol in the presence of boron fluoride acid and water.
/ L, and 0.006 g / L of o-phenanthroline, which is an aromatic cyclic nitrogen compound as the second brightening agent, were added to each of the bright tin plating solutions under the same conditions as in Example 1 to form a sample No. ． It was set to 6.

Example 7 In the tin-lead alloy plating solution used in Example 1 above, 3 mL / L of an amine-aldehyde condensate, which is a conventional brightening agent for direct current electrolytic plating, was used as a first brightening agent. As the brightening agent of No. 2, 0.5 mL / L of a substance obtained by subjecting paraacetaldehyde to a condensation reaction in the presence of boron fluoride acid and water was added, and a bright tin plating solution was added under the same conditions as in Example 1. Sample No. It was set to 7.

Example 8 In the tin-lead alloy plating solution used in Example 1 above, 3 mL / L of a conventional brightening agent for direct current electrolytic plating, amine-aldehyde condensate, was added as a first brightening agent. As a brightener of No. 2, 0.06 g / L of ethyl quinolinium salt was added, and a bright tin plating solution was plated under the same conditions as in Example 1. It was set to 8.

Comparative Example 1 The tin-lead alloy plating solution used in Example 1 above was provided with 20 mL / L of ortho (o-) toluidine / acetaldehyde condensate, 10 mL / L of formalin, and 25 g / L of surfactant as a brightening agent. Sample No. 3 was formed by plating the added conventional bright tin-lead alloy plating solution for direct current by the conventional direct current electrolytic plating method (6 A / dm ² ). It was set to 9.

Comparative Example 2 A film prepared by plating the tin-lead alloy plating solution containing no brightening agent in the above Example 1 by the conventional direct current electrolytic plating method (6 A / dm ² ) was used as a sample N.
o. It was set to 10.

Reference Example 1 To the tin-lead alloy plating solution used in Example 1 above, 20 mL / L of ortho (o-) toluidine / acetaldehyde condensate, 10 mL / L of formalin, and 25 g / L of surfactant were added as brightening agents. A film obtained by plating the added conventional bright tin-lead alloy plating solution for direct current under the same conditions as in Example 1 was used as sample No. It was set to 11.

Reference Example 2 A coating film obtained by plating the bright tin-lead alloy plating solution (containing a brightening agent) used in the above-mentioned Example 1 by using a conventional DC electrolytic plating method (6 A / dm ² ) was prepared. It was set to 12.

Sample No. 1 above. Or No. The gloss ratio, reflow resistance, heat resistance, pinhole, and other properties of the No. 12 plating film are shown in Tables 1 and 2 below.

[0035]

[Table 1]

[0036]

[Table 2]

In the above Tables 1 and 2, the gloss factor indicates the reflectance% of the plating film when the reflectance of the mirror is 100%. The heat resistance indicates the gloss ratio after heating at 150 ° C. for 60 hours, and the lower the gloss ratio, the lower the heat resistance. In the indication of reflow resistance, ⊚ indicates that the film is not offset at all, ◯ is the allowable range, Δ indicates that the film is partially offset, and × indicates that the film is offset on the entire surface. . Pinhole, likewise, has no ◎
◯ means little, and x means very much. The electrodeposition efficiency indicates the adhesion rate% of the plated material to the material to be plated. In the case of electroplating, the uniform electrodeposition property has a current concentration part and a non-concentration part in the product, and the variation of the film thickness due to this current concentration is
0.25 times centered on the set average current density and 2.
Although there is a 5 times difference in current density, it is shown by the ratio of the plating film thickness when plating is performed at this low current density and high current density, and 100% is the best uniform electrodeposition.

As is clear from the results shown in Tables 1 and 2,
Sample No. plated by the direct current electrolytic plating method using a plating solution containing a conventional brightener for direct current is added. The film of 9 is
Specular gloss is obtained and the appearance is excellent. However, this sample N
o. The film of No. 9 has remarkably poor properties such as heat resistance, reflow resistance and pinhole, and it is quite difficult to obtain a film excellent in solderability. Using this conventional plating solution containing a brightening agent for direct current, sample No. The film No. 11 has low values of glossiness and heat resistance, and also has poor reflow resistance. Regarding the reflow resistance, sample N containing no brightener at all
o. 10 is better. However, this sample No.
The film of No. 10 cannot be used because the properties such as gloss ratio, heat resistance and pinhole are extremely poor. Further, even when the plating solution containing the brightening agent for modulated current electrolysis according to the present invention was used, when plating was carried out by the direct current electrolytic plating method, the sample No. 12
There is no effect at all, and the gloss ratio, heat resistance, reflow resistance and pinhole are all obtained by the conventional method. It is clear that the plating film of No. 9 is reduced to the characteristic level.

On the other hand, using the plating solution containing the brightening agent for modulated current electrolysis according to the present invention, Sample No. plated by the modulated current electroplating method was used. 1 to No. Each of the coatings of No. 8 has a high glossiness of 85% or more and has a mirror-like appearance, and also has excellent heat resistance, reflow resistance and pinhole characteristics.

Sample No. The film of Sample No. 2 is Although the electrodeposition efficiency is slightly inferior to that of No. 1, it is characterized in that the uniform electrodeposition property is remarkably excellent. This is because when plated by the high-speed current reversal electrolytic plating method, the plated film thickness of the product is almost the same and there is no variation. Compared to the 500% level of throwing power of 9 is about 1
It can be set to / 2. And the sample No. which added the 2nd brightener further. 3 and sample No. 3 The film of No. 4 shows almost no improvement in the uniform electrodeposition property, but has the characteristics that the electrodeposition efficiency is excellent and the deposition rate of plating can be greatly improved, so that the production rate is remarkably improved. Therefore, it is suitable for products requiring high-speed productivity even if the throwing power is sacrificed to some extent. In addition, the sample No.
5 and sample No. The feature of No. 6 is that, although the electrodeposition efficiency is lowered, a film having an extremely uniform electrodeposition property similar to chemical plating can be obtained. Therefore, the difference in size between terminals and lands is extremely large, especially as seen in a printed circuit board for direct mounting of semiconductor elements, so that it is suitable for plating parts and the like where current concentration is likely to occur during plating.

Sample No. 7 and sample No. 7 The film of 8 is
A substance obtained by subjecting an amine-aldehyde condensate, which is a conventionally used brightener for direct current electrolytic plating, to a first brightener and subjecting paraacetaldehyde to a condensation reaction in the presence of boron fluoride acid and water, or , Which uses ethylquinolinium salt, which is an aromatic cyclic nitrogen compound, as the second brightening agent, and is slightly inferior in reflow resistance and plating solution durability, but has excellent surface gloss, heat resistance, and pinhole characteristics. . In this case, the currently widely used brightening agent can be used as it is as the first brightening agent, and the amount of the used brightening agent is, of course, Sample No. Compared to the amount of brightener used in 1 to 6, the relative amount is large, but it can be reduced to about 1/10 of the amount used in the conventional DC electrolytic plating method, and With the familiarity with management and work procedures,
Very easy to use. Many products require only the heat resistance of the plated terminals in a resin mold or the like and the solderability after heat treatment, and these bright plating solutions are suitable for the production of this type of product. These bright plating solutions are also suitable for conventional DC electrolytic plating.
Similar to Reference Example 2 (Sample No. 12), there is no effect at all.

The ortho (o-) toluidine / acetaldehyde condensate or crotonyl aldehyde as the first brightening agent used in the tin-lead alloy plating solution is used in the presence of paraacetaldehyde, boron fluoride acid and water. ,
Paraacetaldehyde, which is one of the second brighteners, was obtained only after condensation synthesis for a long time in the presence of boron fluoride acid and water. Is almost certainly effective, and it becomes an effective brightener after reacting for 7 days or longer. When the reaction time is 3 days, problems such as abnormal precipitation and the like remain, and the film characteristics tend to be unstable, but there is no practical problem. Condensation methods other than this, for example, condensation using only fluoroboric acid which can serve as a catalyst, and condensation using a conventional sodium carbonate alkaline solution, have no effect, and there is no effect when they are left as they are. For reference, the gloss ratio of the plated film obtained by plating the tin-lead alloy plating solution containing these brighteners by the high-speed current reversal electrolytic plating method (6 A / dm ² ) is shown in Table 3 below.

[0043]

[Table 3]

The plating solution containing the brightening agent for modulated current electrolysis according to the present invention (corresponding to sample No. 1) and the plating solution containing the conventional brightening agent for direct current (sample No. 11)
In the case of performing plating by the high-speed current reversal electrolytic plating method using, the characteristics of each plating film plated at the time of building bath and after the lapse of days from the time of building bath are shown in Table 4 below. The durability of the plating solutions was compared.

[0045]

[Table 4]

Further, in the plating solution (corresponding to Sample No. 1) to which the brightening agent for modulated current electrolysis according to the present invention was added, the amount of the brightening agent added was changed and the high speed current reversal electrolytic plating method (6 A / dm ^{2) was used.} ) And the change in the gloss ratio when plating is performed by the DC electrolytic plating method are shown in Table 5.

[0047]

[Table 5]

As shown in Table 4, the conventional sample No. In the plating solution of No. 11, the solution was decomposed in a very short period of time due to the high-speed current reversal electrolytic plating, and the film characteristics were remarkably deteriorated. Since the plating solution of No. 1 uses a brightener that has been polymerized and stabilized, there is no such phenomenon of deterioration of the film characteristics even after one year, and a stable tin-lead alloy plating film for a long period of time is stable. Can be produced. The reason for this is that the brightener used in the plating solution of the present invention is, for example, an ether-bonding substance mainly having a carbon-oxygen single bond and is extremely stable as described above.

Further, as shown in Table 5, the amount of the brightener is 2 in the bright plating solution prepared by the conventional DC electrolytic plating method.
Although it required 0 to 25 mL / L, the bright plating solution of the present invention is a brightening agent which has an effect of 1/20 of the conventional amount and is extremely effective. Further, since the solubility is low, the same amount as the conventional one cannot be added, and the conventional direct current electrolytic plating method has no effect at all.

As the composition of the second brightening agent, in Examples 5 and 6, o-phenanthroline was used,
In Example 8, the case of using the ethylquinolinium salt was shown, but instead of these, acetoxyquinoline, quinoline, 8-hydroxyquinoline and the above-mentioned
Similar properties were exhibited by using one or a mixture of two or more selected from these, including o-phenanthroline and ethylquinolinium salt.

Further, in each of the above-mentioned embodiments, the case where the high-speed current reversal electrolytic plating is used as the modulation current electrolytic plating method is shown, but other methods such as PR electrolytic plating and pulse electrolytic plating are used. Good. The plating film obtained by these methods is inferior to that obtained by the high-speed current reversal electrolytic plating method, but it is possible to obtain a plating film having far superior characteristics to that obtained by the conventional bright plating solution by the direct current electrolytic plating method. Further, as the tin-based metal plating solution, in the example, the case where the tin-lead alloy plating solution is used is shown, but even if the tin-plating solution or another tin-based alloy plating solution is used, almost the same film characteristics are obtained. To be

The amount of the brightening agent added to the tin-based metal plating solution, including those listed in this example, is effectively in the following range. That is, paraacetaldehyde 0.5
1 to 1 mol of the recondensed substance obtained by reacting 1 mol of a condensate of ortho (o-) toluidine and acetaldehyde in the presence of fluoroboric acid and water.
To 1 g / L, paraacetaldehyde 0.1 to 1
The substance obtained by reacting 1 mol of crotonyl aldehyde having an unsaturated double bond in the presence of boron fluoride acid and water is 0.05 to 5 mL / L, paraacetaldehyde The substance obtained by the condensation reaction in the presence of boric acid and water is 0.05 to 1 mL /
L, and one or a mixture of two or more selected from o-phenanthroline, acetoxyquinoline, ethylquinolinium salt, quinoline, and 8-hydroxyquinoline is preferably 0.005 to 0.2 g / L. is there.

[0053]

EFFECTS OF THE INVENTION The bright tin metal plating solution for modulated current electrolysis according to the present invention does not use a substance having a double bond between carbon and oxygen as a brightening agent added, unlike the conventional case. Since an ether-bonding substance mainly composed of a single bond between carbon and oxygen is used, the brightening agent does not decompose or change due to a remarkable electrolytic action during the electrolysis of modulated current. Then, this brightening agent is approximately 1/20 or less of the brightening agent concentration generally used in the direct current electrolytic plating method, that is, the first brightening agent is 0.05% in the extremely thin diffusion layer formed at the time of modulation current electrolytic plating. Even though the second brightener has an extremely low concentration of several tens to several hundreds of ppm, it exerts a brightening effect effectively by applying a reverse current and instantaneous intermittent pulses.

As a result, it is possible to form a tin and tin-lead alloy plating film having excellent mirror gloss, no pinhole, high heat resistance, high reflow resistance, high solderability, etc., stably for a long period of time. Therefore, the mounting productivity of the printed circuit board, the reliability of the product, the durability, the quality improvement, the defect rate and the cost reduction can be achieved.

The features of the present invention are summarized as follows. The first feature is that the brightening agent used in the present invention is extremely effective only in the modulation current electrolytic plating method and can form a plating film excellent in surface gloss and other characteristics. If this is used for the conventional direct current electrolytic plating method, even if the addition amount is about 10
Even if it is increased by 20 times, it has no effect.

The second feature is that in order to prevent decomposition at the time of modulated current electrolysis in the presence of water using boron fluoride acid as a catalyst,
The reason is that a brightening agent which is completely condensed and has a very high stability is used. Since the carbon-oxygen double bond is etherified and stabilized during this condensation, it exerts a remarkable luster in modulated current electroplating. With a plating solution that uses formalin in combination with ortho (o-) toluidine / acetaldehyde condensate obtained by the conventional direct current electrolytic plating method, the aldehyde component disappears due to oxidation, condensation and decomposition of formalin, etc., especially after standing for about 7 days. , It is always necessary to replenish new formalin etc., like the present invention,
Condensation in fluorinated boronic acid, for example, resulted in conversion of the substance into a meaningless substance as a brightener, and could not be carried out at all.

The third characteristic is that the brightener used in the present invention has an optimum addition amount of about 1/20 or less of the level (several g / L to several tens g / L) of the conventional DC electrolytic plating method. It is effective at low concentrations. this is,
This is because in the present invention, the brightener acts extremely effectively in the thin diffusion layer formed during the modulated current electrolysis.

The fourth characteristic is that the brightening agent used in the present invention is effective in plating solution with any of fluoroboric acid, sulfamic acid and sulfuric acid. The bright tin-based metal plating solution of the present invention can form a plating film having extremely excellent characteristics by modulation current electrolytic plating regardless of the material of the metal to be treated and the type of material.

The fifth feature is that when the condensation synthesis reaction of the brightening agent used in the present invention is carried out, the condensation occurs explosively when it is condensed as a single product under a boron fluoride acid catalyst, which is dangerous. Therefore, the reaction is completed in the industrially available reaction time by allowing water to be present as an appropriate condensation by-product.

As described above in detail, the bright tin-based metal plating solution of the present invention is heat-resistant, solderable, reflow-resistant, with respect to all metal materials by using the modulated current electrolytic plating method. Plating film with excellent corrosion resistance and pinhole characteristics
It is extremely excellent and versatile in that it can be formed efficiently and at low cost. Therefore, the improvement of the characteristics of these plating films can improve the performance, reliability, durability, and productivity of electronic parts, products, and devices, and contributes industrially and socially.

Continuation of the front page (72) Inventor Shinoda Shingo, Misato-mura, Minamiazumi-gun, Nagano 2355-5, Akimori, Misato-mura

Claims (8)

[Claims] 1. Recondensation obtained by reacting 1 mol of a condensate of ortho (o-) toluidine and acetaldehyde with 0.5 to 1 mol of paraacetaldehyde in the presence of fluoroboric acid and water. Using the substance as a brightener, 0.05 to 1 g of the brightener in a tin-based metal plating solution
A bright tin-based metal plating solution for modulated current electrolysis, which is characterized by adding / L. 2. A substance obtained by reacting 1 to 1 mol of paraacetaldehyde with 1 mol of crotonyl aldehyde having an unsaturated double bond in the presence of fluoroboric acid and water. A bright tin-based metal plating solution for modulated current electrolysis, comprising 0.05 to 5 mL / L of the brightening agent added to a tin-based metal plating solution as an agent. 3. A recondensation obtained by reacting 0.5 to 1 mol of paraacetaldehyde with 1 mol of a condensate of ortho (o-) toluidine and acetaldehyde in the presence of fluoroboric acid and water. The substance is the first brightener,
A substance obtained by subjecting paraacetaldehyde to a condensation reaction in the presence of boron fluoride acid and water as a second brightener,
0.05 to 1 g / L of the first brightener and 0.05 to 1 mL of the second brightener in the tin-based metal plating solution
/ L is added to each of the bright tin-based metal plating solutions for modulated current electrolysis. 4. A substance obtained by reacting 1 to 1 mol of paraacetaldehyde with 1 mol of crotonyl aldehyde having an unsaturated double bond in the presence of fluoroboric acid and water. As a second brightener, a substance obtained by subjecting paraacetaldehyde to a condensation reaction in the presence of boron fluoride acid and water as a second brightener is used as a second brightener in a tin-based metal plating solution. 0.05 to 5 mL /
L, a bright tin-based metal plating solution for modulated current electrolysis, wherein 0.05 to 1 mL / L of the second brightening agent is added, respectively. 5. A recondensation obtained by reacting 1 mol of a condensate of ortho (o-) toluidine and acetaldehyde with 0.5 to 1 mol of paraacetaldehyde in the presence of fluoroboric acid and water. The substance is the first brightener,
Aromatic cyclic nitrogen compounds o-phenanthroline, acetoxyquinoline, ethylquinolinium salt, quinoline,
As a second brightening agent, one or a mixture of two or more kinds selected from 8-hydroxyquinoline is used in a tin-based metal plating solution, and the first brightening agent is added in an amount of 0.05 to 1 g / L and the second brightening agent. A bright tin-based metal plating solution for modulated current electrolysis, which comprises adding 0.005 to 0.2 g / L of a brightening agent, respectively. 6. A substance obtained by reacting 1 mol of crotonyl aldehyde having an unsaturated double bond with 0.1 to 1 mol of paraacetaldehyde in the presence of boron fluoride acid and water. The second brightener is one brightener and one or a mixture of two or more selected from aromatic cyclic nitrogen compounds, o-phenanthroline, acetoxyquinoline, ethylquinolinium salt, quinoline, and 8-hydroxyquinoline. As the above, 0.05 to 5 mL / L of the first brightening agent and 0.005 to 0.2 g / L of the second brightening agent are added to the tin-based metal plating solution, respectively. Bright tin-based metal plating solution for modulated current electrolysis. 7. A tin-based metal, wherein an amine-aldehyde condensate is used as a first brightening agent, and a substance obtained by subjecting paraacetaldehyde to a condensation reaction in the presence of fluoroboric acid and water is used as a second brightening agent. In the plating solution, the first brightener 1
To 5 mL / L, the second brightener 0.05 to 1
A bright tin-based metal plating solution for modulated current electrolysis, which is characterized by adding mL / L, respectively. 8. One selected from an aromatic cyclic nitrogen compound, o-phenanthroline, acetoxyquinoline, ethylquinolinium salt, quinoline, and 8-hydroxyquinoline, using an amine-aldehyde condensate as a first brightener. Alternatively, using a mixture of two or more kinds as a second brightener, the first brightener 1 to 5 mL /
L, the second brightener 0.005 to 0.2 g / L
A bright tin-based metal plating solution for modulated current electrolysis, characterized in that