JP3340590B2 - Electrolytic production of lead sulfonate and tin salts for solder plating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrolytically producing a lead sulfonate salt and a tin salt for solder plating which gives a plating film with a reduced number of radioactive α particles, uranium (U), thorium (Th). Lead sulfonate and tin salt whose radioisotope impurity content has been reduced to 50 ppb, a solder plating bath containing these lead salt and tin salt, and a count of radioactive α particles of the resulting plating film of 0.1. The present invention relates to a solder-plated electrodeposit having less than 1 CPH / cm ² .

[0002]

2. Description of the Related Art With the recent remarkable development of the electronics industry, tin and solder plating having good solderability have been applied to electronic components. Conventionally, a borofluoride bath has been used for solder plating.However, fluorine, which is one of the constituent elements of borofluoric acid, is a very toxic element, and at the same time, it is difficult to treat wastewater. Low-toxic organic sulfonates have become widely used in place of borofluorate, and there have been many reports on plating techniques using these organic sulfonates and their additives.
On the other hand, as a process for producing lead salts and tin salts of organic sulfonic acids used in a solder plating solution, a method of producing by heating and dissolving oxides, hydroxides and carbonates of these metals in organic sulfonic acids is known. Has been adopted. However, oxides, hydroxides and carbonates of these metals contain a large amount of uranium (U) and thorium (Th), which are sources of α-rays. In such a case, these impurities are mixed in the lead sulfonate salt and the tin salt, and a large number of α rays are generated from the solder electrodeposit obtained after plating. The present inventors have filed a patent application for an electrolytic production method of a lead salt and a tin salt of an organic sulfonate using an anion exchange membrane with 4 nines of lead and tin metal as anodes (Japanese Patent Publication No. 3-4624). Lead and tin contain uranium and thorium, which are sources of α-rays even in the form of metal. Therefore, the number of radioactive α-particles can be counted to some extent by using the above patented method rather than the usual chemical dissolution method. Although it is possible to obtain a solder-plated electrodeposit having a small number of defects, it is still necessary to further improve the reliability of the memory device in order to obtain high reliability.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a solder plating that suppresses the occurrence of memory errors in a semiconductor in view of the above-mentioned circumstances. By removing the radioactive isotopes uranium, thorium, etc. contained as unavoidable impurities in tin and tin, to provide an electrolytic production method of organic lead sulfonate and tin salt in which the count number of radioactive α particles is reduced. is there.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention uses an electrolytic cell in which an anode chamber and a cathode chamber are separated by a cation exchange membrane and an anion exchange membrane, and uses the following formula (I) (X ₁ ) _n -R- SO ₃ H Formula (I) (where R represents a C ₁ -C ₅ alkyl group, and X ₁
Represents a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, a carboxyl group or a sulfonic acid group, and may be at any position of the alkyl group, and n is an integer of 0 to 3. Acid and the following formula (II)

Embedded image (Where X ₂ represents a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, an aldehyde group, a carboxyl group, a nitro group, a mercapto group, a sulfonic acid group or an amino group, or two X ₂ are a benzene ring Can be combined to form a naphthalene ring, and m is an integer of 0 to 3) using a solution of an organic sulfonic acid selected from the group consisting of aromatic sulfonic acids, and using lead or tin as an anode and, Thus Namarimata a DC voltage to the anode and the electrolytic solution is applied to the cathode Ri Do from dissolving tin, uranium, DOO
The content of radioisotope impurities such as lium is less than 50ppb.
Electrolytic production how the reduced sulfone San'namarishio or tin salts fully related.

[0005] The present invention further relates to a lead or tin salt of an organic sulfonic acid having a reduced content of radioisotope impurities such as uranium and thorium obtained by the above-mentioned production method to 50 ppb, such an organic sulfonic acid. A solder plating bath containing a solution of a lead salt and a tin salt, and a solder plating electrodeposit having a radioactive α particle count of less than 0.1 CPH / cm ² in a plating film obtained from the plating bath.

[0006]

DETAILED DESCRIPTION OF THE INVENTION Here, an example of an electrolysis apparatus that can be used to carry out the electrolytic production method of the present invention is described in FIG. In FIG. 1, 2 is provided in an electrolytic cell 1 for producing a lead sulfonate salt and a tin sulfonate salt.
A single cathode 4, for example a platinum plate, is provided, between which an anode 2, for example a lead or tin bar, is provided, around which the granular lead or tin 3 to be dissolved is arranged. Further, a multi-layer electrolytic cell in which a cation exchange membrane 5 and an anion exchange membrane 6 are arranged between the anode 2 and the cathode 4 is used. A shielding plate 7 is provided between the anode 2 and the cathode 4 to define an anode chamber and a cathode chamber, respectively. An electrolytic solution 8 composed of a solution of an organic sulfonic acid is introduced into the anode chamber and the cathode chamber, and a circulation pump such as a chemical pump 10 and a heat exchanger 11 are provided.
Stirring and cooling. A DC power supply 9 is connected to the anode and the cathode. The solution of the organic lead sulfonic acid salt or the tin sulfonic acid salt obtained by the electrolysis is taken out from the product outlet 12. As conditions for the electrolysis according to the invention, the current density for the membrane is between 1 and 50 A / dm ² , preferably between 5 and 30 A / dm ² .
A / dm ² , and the liquid temperature is 10 to 50 ° C., preferably 2
0 to 40 ° C., and the extreme voltage is 0.5 to 20 V, preferably 1 to 5 V. These electrolysis conditions and operations are such that the number of radioactive α particles in the plating film obtained is 0.1 C
It can be arbitrarily changed to obtain an organic lead sulfonate and tin salt having a pH of not more than PH / cm ² .

The electrolytic solution used in the present invention has the following formula (I) (X ₁ ) _n -R-SO ₃ H Formula (I) (where R represents a C ₁ -C ₅ alkyl group; X ₁
Represents a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, a carboxyl group or a sulfonic acid group, and may be at any position of the alkyl group, and n is an integer of 0 to 3. Acid and the following formula (II)

Embedded image (Where X ₂ represents a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, an aldehyde group, a carboxyl group, a nitro group, a mercapto group, a sulfonic acid group or an amino group, or two X ₂ represent a benzene ring Which can form a naphthalene ring together and m is an integer of 0 to 3), and is a solution of an organic sulfonic acid selected from the group consisting of aromatic sulfonic acids. The concentration of the organic sulfonic acid in the electrolytic solution can be appropriately selected according to the concentration of the target sulfonic acid salt. Generally, the concentration of sulfonic acid is 5 to
It is 50%, preferably 25 to 40%.

Examples of these organic sulfonic acids include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid,
-Propanesulfonic acid, butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2
-Hydroxypentanesulfonic acid, 1-carboxyethanesulfonic acid, 1,3-propanedisulfonic acid, arylsulfonic acid, 2-sulfoacetic acid, 2- or 3-sulfopropionic acid, sulfosuccinic acid, sulfomaleic acid, sulfofumaric acid, Benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, nitrobenzenesulfonic acid,
Sulfobenzoic acid, sulfosalicylic acid, benzaldehyde sulfonic acid, p-phenolsulfonic acid, phenol-
2,4-disulfonic acid and the like. The concentration of these sulfonic acids is 5-80%, preferably 25-50%,
They can be used alone or as a mixture of two or more.

The lead and tin used as the anode are preferably those having a grade of 3 nines or more, and may have any shape, but are preferably granular or spherical. As the cathode material, those which are inert to the electrolytic solution are preferable, and for example, plate-like platinum, nickel, titanium, stainless steel, carbon or platinum-plated platinum is preferable.

[0010] The cation exchange membrane and the anion exchange membrane must basically have low electric resistance and good acid resistance, durability and heat resistance. In addition, the cation exchange membrane must allow dissolved lead or tin cations to pass from the anode, and the anion exchange membrane must act to prevent lead or tin cations from migrating to the cathode.
As an exchange membrane that can be used, for example, C manufactured by Tokuyama Soda
MS, C66-10F (cation), ACLE-5P,
AM-2 (anion) and the like.

The reason why the radioactive α-particles are reduced in the present invention is not desired to be bound by any particular theory. However, while lead or tin cation dissolved from the anode exists in the electrolyte as it is, uranium and thorium do not. It dissolves in the electrolyte to form an anion complex, so that it does not pass through the cation exchange membrane, only lead, tin and hydrogen ions pass through it, while the anion exchange membrane leads to lead or tin ions Is prevented from migrating to the cathode, and as a result, the solution of the lead or tin salt from which uranium and thorium are removed is continuously taken out from between the cation exchange membrane and the anion exchange membrane. Seem.

The lead or tin salt of an organic sulfonate obtained by the electrolytic production of the present invention is obtained as a solution of a lead salt or a tin salt dissolved in an electrolytic solution, and therefore contains free sulfonic acid. . Generally, the resulting solution is 5-25% by weight, preferably 10-1% by weight, as Pb ²⁺ , in the case of lead salts.
It is an aqueous solution containing 5% by weight of lead sulfonic acid salt, 5 to 30% by weight, preferably 10 to 20% by weight of free sulfonic acid. In the case of a tin salt, 5 to 25% by weight, preferably 10 to 15% by weight of tin sulfonate as Sn ²⁺ ,
It is an aqueous solution containing 5 to 30% by weight, preferably 10 to 20% by weight of free sulfonic acid. The aqueous solution thus obtained can be used directly for solder plating, but usually the concentrations of lead and tin and the concentration of free sulfonic acid are adjusted to obtain the desired solder plating.

Thus, the solution of a lead or tin salt of an organic sulfonic acid of the present invention can be used for solder plating in a generally known sulfonic acid bath. For example,
The solder plating bath has the following composition. Organic sulfonic acid lead salt (as Pb ²⁺ ): 0.1 g to 80
g / l, preferably 0.5-60 g / l tin organosulfonate (as Sn ²⁺ ): 0.1 g-80
g / l, preferably 0.5-60 g / l free sulfonic acid: 50-200 g / l, preferably 10
0 to 150 g / l A well-known plating additive such as a surfactant can be added to such a plating bath. As plating conditions in such a case, the current density is 0.2 to 50 A.
/ Dm ^2, preferably from 1 through 15A / dm ^2, temperature 5 to 30 ° C., preferably 15-25 ° C.. When solder plating is performed using the lead organic sulfonate and tin salt produced by the electrolytic production method of the present invention, the number of radioactive α particles in the resulting plating film can be reduced to less than 0.1 CPH / cm ^2. it can. This is, as mentioned above,
This is because uranium and thorium contained as inevitable impurities in lead and tin, which are the main components of the solder film, have been reduced to less than 50 ppb by the electrolytic method of the present invention.

[0014]

The present invention will now be described by way of examples. However, the present invention is not limited to these examples, and as described above, the number of radioactive α-particles in the plating film obtained is not more than 0.1.
It can be arbitrarily changed according to the gist of obtaining an organic lead sulfonate and a tin salt of less than 1 CPH / cm ² .

Example of Electrolytic Production of Organic Sulfonate Production Example 1 This example illustrates the production of lead methanesulfonate using an electrolytic production apparatus as shown in FIG. Electrolysis cell thickness 5
mm acrylic plate, capacity of 250 ml anode chamber, capacity of 100 ml product chamber, capacity of 324 m
1 × 2 cathodic compartments, 5 × 18 = 90 cm ² cation exchange membranes (C66-10F), anion exchange membranes (AC
LE-5P), 2.5m inside diameter at 2.5mm intervals
It is made by setting two shield plates each having a hole of m. Then, a lead rod for contact having a purity of 99.9% is placed in the center of the anode chamber and granular lead of the same 99.9% is put in the periphery thereof, and ^two 0.9 dm ² titanium plates are used as cathodes. Then, a solution of methanesulfonic acid having a predetermined concentration is put in the cathode chamber, circulation and cooling are performed with the flow rate of the anolyte at 3.3 L / min and the flow rate of the catholyte at 2.2 L / min, and the anode and the cathode are supplied. Electrolysis was performed by applying a DC voltage. The obtained results were obtained by electrolysis conditions, concentrations of free acid (FA) and Pb ²⁺ in each solution of the product room and the cathode room before and after electrolysis, concentrations of U and Th in the solution of the product room after electrolysis, and Pb. Are shown in Table 1 together with the dissolution efficiency.

[Table 1]

As a comparative example, Japanese Patent Publication No. 3-4624
The electrolysis of lead was carried out as described in Production Example 1 using an electrolysis cell as described in No. 2, that is, an electrolysis cell using only an anion exchange membrane between the anode and the cathode. The results obtained are shown in Table 1-1.

[Table 2]

Preparation Example 2 This example illustrates the preparation of tin methanesulfonate. The configuration of the electrolytic cell used was the same as that of Production Example 1, except that a 99.9% contact tin bar was provided on the anode and 9
Electrolysis was performed by adding 9.9% of granular tin. Table 2 shows the obtained results.

[Table 3]

As a comparative example, Japanese Patent Publication No. 3-4624
The electrolysis of tin was carried out as described in Production Example 2 using an electrolysis cell as described in No. 2, that is, an electrolysis cell using only an anion exchange membrane between the anode and the cathode. The results obtained are shown in Table 2-1.

[Table 4]

Preparation Example 3 This example illustrates the preparation of tin 2-hydroxypropanesulfonate. The configuration of the electrolytic cell used was the same as that of Production Example 1, except that 99.9% of a tin rod for contact and 99.9% of granular tin were placed around the anode and 2-hydroxypropane as an electrolytic solution. Electrolysis was performed using a solution containing sulfonic acid. Table 3 shows the obtained results.

[Table 5]

As a comparative example, Japanese Patent Publication No. 3-4624
The electrolysis of tin was carried out as described in Production Example 3 using an electrolysis cell as described in No. 2, i.e., an electrolysis cell using only an anion exchange membrane between the anode and the cathode. The results obtained are shown in Table 3-1.

[Table 6]

Electrolysis was carried out in the same manner as described in Production Example 3 above, except that lead was used in place of the tin rod for contact and granular tin, to produce a lead salt of 2-hydroxypropanesulfonic acid. .

Preparation Example 4 This example illustrates the preparation of lead p-phenolsulfonate. The configuration of the electrolytic cell used was the same as that of Production Example 1, except that 99.9% of a lead rod for contact was placed in the anode and 99.9% of granular lead was also placed around the rod, and p-phenol sulfone was used as the electrolytic solution. Electrolysis was performed using a solution containing an acid. Table 4 shows the obtained results.

[Table 7]

As a comparative example, Japanese Patent Publication No. 3-4624
The electrolysis of lead was carried out as described in Production Example 4 using an electrolysis cell as described in No. 2, ie, an electrolysis cell using only an anion exchange membrane between the anode and the cathode. The results obtained are shown in Table 4-1.

[Table 8]

Further, in the same manner as in the method described in Production Example 4, electrolysis was performed using tin instead of the lead bar for contacts and granular lead to produce tin p-phenolsulfonate.

Example of Solder Plating Each of the lead sulfonic acid salt and the tin salt taken out of the product chamber of the electrolytic production apparatus described in the above production example was dissolved in an aqueous sulfonic acid solution, and an appropriate surfactant (for example, polyoxysilane) was used. Ethylene laurylamine) was added to prepare a solder plating bath having the composition shown in Table 5 below. Using this bath, using an insoluble anode platinum-plated on titanium,
The plating was performed by connecting a DC power supply using the copper plate as a cathode.
The obtained results were used together with the composition of the plating solution, the plating conditions, the composition of the electrodeposit and the count number of the radioactive α-particles in the following 5th.
See the table.

[0026]

[Table 9]

[Table 10]

In the embodiment of the solder plating described above, Comparative Example 1 uses an electrolytic cell as described in JP-B-3-4624, that is, using only an anion exchange membrane between an anode and a cathode, and performing electrolysis. A plating bath was prepared by preparing a solder plating bath from the produced lead methanesulfonate and tin methanesulfonate. In Comparative Example 2, a solder plating bath was prepared from lead methanesulfonate and tin methanesulfonate produced by heating and dissolving lead oxide and tin oxide in an aqueous methanesulfonic acid solution, and plating was performed. . Although the count number of α particles in Comparative Example 1 was suppressed to some extent as compared with that prepared from the oxide of Comparative Example 2, a lower count number of α particles was obtained from the plating bath of Example of the present invention. You can see that it is.

[0028]

According to the present invention, an anode cell and a cathode cell are separated by a cation exchange membrane and an anion exchange membrane, and anodic dissolution of lead and tin metal having a grade of 3 or more is used. The organic lead sulfonate and tin salt have a radioisotope impurity content of 50p such as uranium and thorium.
pb. Therefore, from a solder plating bath using such a lead salt of an organic sulfonate and a tin salt, it is possible to form a solder film that significantly suppresses the occurrence of memory errors.
It becomes possible to apply a solder plating to components of a semiconductor device such as a memory of 6K or more and a super LSI.

[Brief description of the drawings]

FIG. 1 is a system diagram of an electrolysis apparatus that can be used in the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolysis cell 2 Lead or tin rod of anode contact 3 Granular lead or tin 4 Platinum cathode 5 Cation exchange membrane 6 Anion exchange membrane 8 Electrolyte

──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshiharu Matsuda 1-11-10 Minami Kobayamacho, Ube City, Yamaguchi Prefecture (72) Masaichi Yoshimoto 5-18-7 Izumidai, Kita-ku, Kobe City, Hyogo Prefecture ) References JP 3-4624 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25B 1/00-15/08 C25D 3/56 C25D 21/14 H01L 23/50

Claims (4)

(57) [Claims] (1) a cation exchange membrane and an anode chamber;
Use an electrolytic cell separated by a nonion exchange membrane and use it as an electrolyte.
The following formula (I) (X₁)_n -R-SO₃H Formula (I) (where R is C₁~ C₅X represents an alkyl group₁
Is a hydroxyl group, an alkyl group, an aryl group, an alkylaryl
Group, a carboxyl group or a sulfonic acid group, and
It may be at any position of the alkyl group, and n is an integer of 0 to 3.
And an aliphatic sulfonic acid represented by the following formula (II):(Where X₂Represents a hydroxyl group, an alkyl group, an aryl group,
Alkylaryl group, aldehyde group, carboxyl group,
Toro, mercapto, sulfonic or amino groups
I, or two Xs₂Is combined with the benzene ring
Which can form a phthaline ring, and m is an integer of 0 to 3).
Use a solution of organic sulfonic acid and use lead or tin as anode
And then apply DC voltage to the anode and cathode
Because lead or tin is dissolved in the liquidUranium, uranium
The content of radioisotope impurities such as lium is less than 50ppb.
Fully reducedElectrolytic production of lead sulfonate or tin saltOne
Law. 2. A uranium claim 1 organic sulfonic lead salts and in tin obtained by the production how according, organic sulfonic acids radioisotope content of impurities such as thorium and less than 50ppb Lead salts and tin salts. 3. The composition according to claim 2, which contains the lead salt and tin salt of organic sulfonic acid according to claim 2 and free organic sulfonic acid, and has a radioactive α particle count of less than 0.1 CPH / cm ^2. Solder plating bath. 4. A plating film obtained from the plating bath according to claim 3, wherein the counted number of radioactive α particles is 0.1 CPH /
Electroplated solder plating having a size of less than ² cm ² .