KR20130029358A - Method of removing impurities from plating liquid - Google Patents

Abstract

PURPOSE: A method of removing impurities from plating liquid is provided to enable to reduce impurities at low concentration without a special device for removing the impurities from electroless tin plating liquid. CONSTITUTION: A method of removing impurities from plating liquid comprises; a step for forming precipitate of impurities by adding aromatic organic sulfonic acid, a hydrate thereof, and a salt thereof and cooling the same; and a step for removing the precipitate form the electroless tin plating liquid.

Description

METHOD OF REMOVING IMPURITIES FROM PLATING LIQUID}

The present invention relates to a method for removing impurities from a tin plating liquid. More specifically, the present invention relates to a method for removing impurities from a tin plating solution by forming a precipitate of impurities and removing impurities from the tin plating solution without using a special apparatus.

In recent years, electroless tin plating has been widely used for plating mechanical components, flexible substrates, printed wiring boards and circuit patterns for electronic components. Electroless tin plating of these articles is often performed as tin substitution plating on copper or copper alloys. When tin-substituted plating is performed on copper or a copper alloy, the substituted copper becomes copper ions to be dissolved in the plating solution, and copper ions accumulate as the plating proceeds. The copper ions thus accumulated form an unacceptable plated film and the bath must be replaced with a new one by degrading the bath's performance.

As a method of treating a plating liquid, a batch method and a feed-and-bleed method are known. The placement method is to replace the bath with a new plating bath when the bath is old; In electroless tin plating baths, the baths must be replaced each time the copper concentration rises and the bath deteriorates. This causes problems such as an increase in the number of manufacturing operations of the bath, a decrease in productivity, and an increase in the cost of treating the waste tank. In addition, the flow rate increase and decrease method is a method in which plating proceeds while the plating liquid overflows. Copper can be removed from the system without interrupting the plating operation, but a large amount of plating liquid must be replenished, which adds cost.

Various methods have been proposed to solve these problems. For example, in Japanese Unexamined Patent Application No. 5-222540, a part of the plating liquid is taken, and the copper-thiourea complex is cooled and precipitated in the tank, the copper-thiourea complex is removed by filtration, and the filtrate is returned to the plating tank. . Another method is described in Japanese Unexamined Patent Application No. 2002-317275, where the same operation as in No. 5-222540 was performed; The plating solution is cooled to 40 ° C. or lower to precipitate the copper-thiourea composite, which is filtered off.

Another method is described in Japanese Unexamined Patent Application No. 10-317154, in which an anode, a cathode and a cation / anion exchange membrane were provided in a regeneration cell. In the regeneration cell, copper is electrodeposited on the anode, and tin ions passing through the cation exchange membrane are added to the plating solution after electrolysis and returned to the plating tank. In addition, a method of oxidizing and decomposing a copper-thiourea composite is described in Japanese Unexamined Patent Application No. 4-276082.

However, according to the study by the present inventors, the copper removal according to the methods of 5-222540 and 2002-317275 turned out to be insufficient. Therefore, there is a need for a method of removing copper to lower the concentration. The method of 10-317154 requires regeneration of the electrolysis cell and the apparatus is complex. In addition, the method described in 4-276082 requires reagents and apparatus for oxidizing and degrading copper-thiourea complexes. Therefore, there is still a need for an improved method for removing impurities from tin plating solutions.

Summary of the Invention

Adding an aromatic organic sulfonic acid or a salt thereof to an electroless tin plating solution containing a nonionic surfactant and a thiourea or thiourea compound, and cooling to form a precipitate of impurities; A method is provided that includes removing precipitation of impurities from an electroless tin plating solution.

In this way it is possible to remove impurities from the tin plating liquid or to reduce impurities to a lower concentration than conventional methods without requiring a special device for removing impurities from the electroless tin plating liquid.

The present inventors have steadily studied to solve this problem, and found that by adding an aromatic organic sulfonic acid or a salt thereof to an electroless tin plating solution containing a nonionic surfactant and a thiourea or a thiourea compound, and cooling to form a precipitate It has been found that the concentration of impurities in the electroless tin plating solution can be reduced to lower concentrations than conventional methods.

In one aspect of the present invention, the process is performed by adding an additive containing aromatic organic sulfonic acid or a salt thereof to an electroless tin plating solution containing a nonionic surfactant and a thiourea or thiourea compound, and cooling to form a precipitate by Removing impurities from the tin plating solution.

In another aspect of the invention, the process comprises electroless tin plating on copper or a copper alloy using the electroless tin plating solution mentioned above, followed by electroless containing a nonionic surfactant and a thiourea or thiourea compound. Adding an additive containing an aromatic organic sulfonic acid or a salt thereof to the tin plating liquid and regenerating the electroless tin plating liquid by removing the precipitate formed by cooling.

In another aspect of the invention, the method includes forming an electroless tin plated film using an electroless tin plating solution containing a nonionic surfactant and a thiourea or thiourea compound; From the plating tank in which the above-mentioned electroless tin plating is performed, part or all of the plating liquid is recycled to the above-mentioned plating tank by a solid / liquid separation device, and an additive containing an aromatic organic sulfonic acid or a salt thereof is mentioned. The precipitate, which is added to the plating liquid and formed by cooling, is captured and removed by the solid / liquid separation device mentioned above.

In another aspect of the invention, the method comprises a main tank in which electroless tin plating is performed, a settling tank in which precipitation is formed, a circulation pipe connecting the main tank and the settling tank so that the electroless tin plating solution can be circulated, and a settling tank A solid / liquid separation device installed between the main tank and the main tank, and is electrolessly mounted on the article to be plated using a number of tank plating devices using a nonionic surfactant and a tin plating solution containing a thiourea or thiourea compound. Performing tin plating; The process comprises solid / liquid separation of (A) adding an additive containing an aromatic organic sulfonic acid or salt thereof to the tin plating liquid in the precipitation tank, (B) cooling the tin plating liquid and (C) the precipitation formed by cooling. Capturing using the device; The steps are carried out in the order (A), (B), (C) or (B), (A), (C).

In another aspect of the present invention, the method comprises a plating tank in which a plating liquid is stored and electroless tin plating is performed, a recycling pipe connected to the plating tank in a manner in which part or all of the plating liquid can be recycled, a recycling path of the plating liquid. Using a single tank plating device having a solid / liquid separation device, and a temperature control device for cooling or heating the plating liquid in the plating tank, and using a tin plating liquid containing a nonionic surfactant and a thiourea or thiourea compound. Performing electroless tin plating on the article to be plated; This method comprises the steps of immersing an article to be plated in a plating liquid in a plating liquid, adding an additive containing an aromatic organic sulfonic acid or a salt thereof to the plating liquid and forming a precipitate by cooling, and forming the precipitate formed by the solid / liquid mentioned above. Removing from the plating liquid using a separation device.

In a further aspect of the invention, the method comprises treating an electroless tin plating solution containing a nonionic surfactant and a thiourea or thiourea compound and used for electroless tin plating of copper or copper alloys; In the treatment method of the plating liquid, the copper ion concentration in the above-mentioned plating liquid is reduced by adding an additive containing an aromatic organic sulfonic acid or a salt thereof to the plating liquid, and cooling to form a precipitate.

The method of the present invention can reduce the impurities in the tin plating liquid to a lower concentration than the conventional method without using a special apparatus for removing impurities from the electroless tin plating liquid. In addition, by removing impurities, the plating liquid can be used for a long time, and the number of times of discarding the plating liquid and manufacturing a new bath is greatly reduced. Therefore, it greatly contributes to industrial productivity.

DETAILED DESCRIPTION OF THE INVENTION

In the specification and claims, ° C means degrees Celsius; g means gram; L means liter; ml means milliliters; dm stands for decimeter; Μm means micron or micrometer. Unless otherwise stated, all amounts are in weight percent. In the specification and claims, "plating solution", "plating solution" and "plating bath" have the same meaning and are used interchangeably. In addition, in the specification and claims, the term “tin plating liquid” does not mean only “tin plating liquid”; It also includes tin alloy plating liquid. Likewise, the term "electroless tin plating liquid" does not only mean "electroless tin plating liquid", but also includes "electroless tin alloy plating liquid".

In the present invention, the related plating liquid is a tin plating liquid; Electroless tin plating solutions are particularly preferred, and tin plating solutions in which tin substitution plating (or tin alloy substitution plating) on copper or copper alloy can be performed are more preferred. At this time, as mentioned above, the terms "tin plating liquid" and "electroless tin plating liquid" also include those containing other metal components in addition to tin. The tin plating liquids mentioned above contain thiourea or thiourea compounds as water soluble tin salts or water soluble tin salts and other metal salts, nonionic surfactants, and complexing agents.

The water soluble tin salt used in the tin plating solution can be of any type as long as it is soluble in water when the plating solution is made. For example, tin sulfate, stannous chloride, borosilicate, tin alkane sulfonate, tin alkanol sulfonate, and the like can be used.

In addition, examples of other metal salts that can be used with the water-soluble tin salts include salts such as lead, copper, silver, bismuth or cobalt. Specific examples thereof include lead chloride, lead acetate, lead alkane sulfonate, copper chloride, silver nitrate, bismuth chloride, cobalt sulfate, and the like.

The total amount of tin and non-tin metal components in the plating solution is usually present as metal ions in the range of 10 to 100 g / L, preferably 30 to 50 g / L.

Acids may be added to the tin plating solution to dissolve tin or other metal components other than tin. Acids which may be used include sulfuric acid, hydrochloric acid, alkanesulfonic acid, alkanol sulfonic acid, aromatic sulfonic acid and the like. These acids may be used individually or in combination of two or more. The total amount of acid added to the plating liquid is usually in the range of 1 to 300 g / L, preferably 50 to 100 g / L.

The tin plating liquid used in the present invention includes a thiourea or a thiourea compound. They can act as complexing agents of dissolved metals such as copper. From an electrochemical point of view, thiourea or thiourea compounds are well known in the industry as members of components that allow substitutional plating of tin on copper or copper alloys, but are not theoretically possible for standard electrode potentials. The thiourea used may be thiourea, which is usually obtainable. Commercial thioureas can also be used.

Thiourea compounds include thiourea derivatives such as 1-methylthiourea, 1,3-dimethyl-2-thiourea, trimethylthiourea, diethylthiourea, N, N-diisopropylthiourea, 1 (3 -Hydroxypropyl) -2-thiourea, 1-methyl-3- (3-hydroxypropyl) -2-thiourea, 1-methyl-3- (3-methoxypropyl) -2-thiourea, 1 , 3-bis (3-hydroxypropyl) -2-thiourea, allylthiourea, 1-acetyl-2-thiourea, 1-phenyl-3- (2-thiazolyl) thiourea, benzyl isothiourea, Hydrochloride, 1-allyl-2-thiourea, 1benzoyl-2-thiourea and the like. The thiourea or thiourea compounds mentioned above may be used individually or in combination of two or more. The amount of thiourea or thiourea compound is usually in the range from 50 to 250 g / L, preferably from 100 to 200 g / L.

The tin plating liquid used in the present invention contains a nonionic surfactant. Examples of these nonionic surfactants include nonionic surfactants such as octylphenol, alkylamines, alkyl ethers, block polymers, naphthyl ethers, and the like. Specific examples thereof include polyoxyethylene octyl phenol, polyoxyether [ sic ] β-naphthyl ether, polyoxyethylene alkylamine, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene cetyl ether and the like. Especially preferred are polyoxyethylene alkyl ethers, polyoxyethylene octyl phenols, and polyoxyethylene alkylamines.

One or two or more of these nonionic surfactants may be used. The amount of these nonionic surfactants used is usually in the range of 1 to 100 g / L, preferably 5 to 50 g / L.

The tin plating liquid may contain an antioxidant, in addition to the above-mentioned components as necessary. Examples of antioxidants include catechol, hydroquinone and hypophosphorous acid.

Substituted plating, i.e. electroless tin plating, is usually performed by making a plating bath, adjusting the temperature in the range of 50 to 75 DEG C, and then immersing a plated product having a metal such as copper or a copper alloy on the surface for 20 to 300 seconds. Is performed. Tin substitutes a metal such as copper on the surface of the plated product to form a tin film, and metal such as copper on the plated product is dissolved in the plating solution instead of tin ions. Therefore, tin is reduced in the plating liquid as the plating proceeds. It is also believed that thiourea or thiourea complexing agents form complexes with copper or other metals on the plated product, and that the thiourea or thiourea compounds decrease as the plating proceeds. In addition, the acid and other components are reduced as the plated article is pulled out, i.e. picked up, and also decreases as the plating proceeds. As the plating proceeds, these components which are reduced in the plating liquid are replenished in an appropriate manner. However, as the plating proceeds, eluting metals such as copper increase and accumulate in the bath; As a result, the plating film is degraded or the performance of the bath is degraded.

The present invention adds an aromatic organic sulfonic acid or a salt thereof (hereinafter simply referred to as "aromatic organic sulfonic acid") to a tin plating liquid containing a nonionic surfactant, and then cooled to contain an eluting metal such as copper as an impurity. It is characterized by forming a precipitate to suppress the accumulation of an eluting metal such as copper in the plating liquid. By adding an aromatic organic sulfonic acid to the plating liquid and then cooling the plating liquid, an eluting metal complex such as a copper ion complex dissolved in the plating liquid may form a precipitate so that the concentration of eluting metal ions such as copper ions in the plating liquid may be reduced. In addition, "cooling to form a precipitate" refers to an aromatic sulfonic acid after adding an additive containing an aromatic sulfonic acid to the plating liquid and then precipitating the precipitate by cooling, and cooling the plating liquid in a range where precipitation does not precipitate. It also includes the case where an additive is added and precipitation is precipitated.

After precipitation is formed by the method of the present invention, the concentration of the eluting metal, such as copper, in the plating liquid is much lower than that according to the method of the prior art. The detailed reaction mechanism is unknown, but the solubility of the thiourea or thiourea compound complex when metal ions eluted, e. It is believed that this is because is lowered at low temperatures to form a precipitate. Nonionic surfactants are believed to contribute in part to the precipitation formation with aromatic organic sulfonic acids; As the nonionic surfactant, specific ones can be selected to allow the precipitate to be formed more efficiently.

As mentioned above, aromatic organic sulfonic acids or salts thereof are contained in the additives added to the tin plating liquid of the present invention. In the specification and claims, the term "aromatic organic sulfonic acid" refers to aromatic organic sulfonic acids and / or these additives. In addition, the term "comprising aromatic organic sulfonic acids or salts thereof" refers to both aromatic organic sulfonic acids or salts of aromatic organic sulfonic acids, as well as to include both. Examples of the aromatic organic sulfonic acid include phenol sulfonic acid, benzene sulfonic acid, toluene sulfonic acid and naphthalene sulfonic acid, as well as hydrates of the aforementioned aromatic organic sulfonic acids. In addition, the salts of aromatic organic sulfonic acids can be any desired salts, such as sodium, potassium, ammonium, and the like. Aromatic organic sulfonic acids and salts thereof can be used as mixtures.

Additives containing aromatic organic sulfonic acids or salts thereof may also contain components other than aromatic organic sulfonic acids. For example, components consumed or reduced during plating, such as nonionic surfactants, thioureas, thiourea compounds, and acids may be included in these additives, and the addition of these additives may cause the components to be replenished in the plating solution. Can be. In addition, the additive may be a solid or a liquid; For example, the additive may be in the form of an aqueous solution in which aromatic organic sulfonic acid and other optional components are dissolved in water. Making the additive an aqueous solution facilitates control of the amount of aromatic organic sulfonic acid and other optional components added.

The amount of the additive added is such that the concentration of the aromatic organic sulfonic acid or salt thereof in the tin plating solution is in the range of 5 to 200 g / L, preferably 20 to 100 g / L, particularly preferably 50 to 100 g / L. . If the usage is small, no precipitation will occur. In order to obtain sufficient precipitation, it is preferable to allow the aromatic organic sulfonic acid or its salt to be used in an amount such that the concentration is 20 g / L or more. Too much usage will degrade Joe's performance; Deterioration of the state of tin, lowering of the precipitation rate, and the like.

The amount of additive added is preferably determined by the copper concentration in the bath. To remove 1 g of copper, 1 to 30 g of aromatic organic sulfonic acid or a salt thereof, preferably 1 to 20 g, and particularly preferably 2 to 10 g, are added. If the usage is small, no precipitation will occur. If the amount used is too high and aromatic organic sulfonic acid remains in the bath after copper removal, the performance of the bath will be degraded; Deterioration of the state of tin, lowering of the precipitation rate, and the like.

In the first method of the present invention, an additive containing an aromatic organic sulfonic acid or a salt thereof is added to an electroless tin plating solution containing a nonionic surfactant and a thiourea or a thiourea compound, and cooled to form a precipitate to remove impurities from the plating solution. How to remove.

At this time, the tin plating liquid to which the additive containing aromatic organic sulfonic acid is added is preferably one already used for tin plating, in particular electroless tin plating. In the case of electroless tin plating, this may be a plating liquid after the electroless tin plating treatment is completed, or a plating liquid in which the electrolytic tin plating treatment is an intermediate step, as long as it is a liquid used for electroless tin plating. Examples of impurities may be copper and other metals eluted from the plated article, such as nickel, zinc, chromium, molybdenum, tungsten and the like. The impurity is especially copper; Copper can be efficiently removed from the plating liquid by the present invention. As mentioned above, when an additive containing an aromatic organic sulfonic acid is added to the plating solution where plating is used and the concentration of the eluting metal such as copper is increased, insoluble matter containing the eluting metal such as copper is precipitated by cooling. Removing these undissolved components can remove the eluting metal, such as copper, from the plating liquid. In order to remove undissolved components, any desired method may be used, such as filtration, sedimentation and centrifugation.

The second method of the present invention is carried out by electroless tin plating on copper or copper alloy using the electroless tin plating solution mentioned above, followed by electroless tin plating solution containing a nonionic surfactant and a thiourea or thiourea compound. An additive containing an aromatic organic sulfonic acid or a salt thereof is added to the mixture, and the precipitate formed by cooling is removed to regenerate the plating solution.

As described above, an additive containing aromatic organic sulfonic acid can be added to the plating liquid to remove precipitated precipitate and cool to remove impurities, especially eluted metals such as copper, from the plating liquid. After removing the precipitate, the plating liquid can be reused; Other components that have been consumed or reduced can be supplemented to continue using the plating liquid. Therefore, it is not necessary to discard the passed plating liquid and the industrial productivity can be improved. The components consumed or reduced can be supplemented by adding components to be supplemented, such as nonionic surfactants, thioureas, thiourea compounds, tin, acids and the like to additives containing aromatic organic sulfonic acids.

The third method of the present invention uses an electroless tin plating solution containing a nonionic surfactant and a thiourea or thiourea compound; Part or all of the plating liquid removed from the plating bath in which the electroless tin plating is performed is recycled to the plating bath by a solid / liquid separation device, and an additive containing an aromatic organic sulfonic acid or a salt thereof is added to the plating solution and cooled by It is a method of forming an electroless tin plating film which captures the produced precipitate and removes it by the solid / liquid separation device.

In this method, the plating liquid can also be cooled to a temperature at which the additive containing aromatic organic sulfonic acid is added and the temperature does not appear, or to the temperature at which the precipitate is formed after the addition of the aromatic organic sulfonic acid is added. have. Recycling of the electroless tin plating solution is preferably performed when the plating operation is stopped. In addition, additives containing aromatic organic sulfonic acids can be added when the plating operation is stopped, and the consumption or reduced necessary components of the plating liquid are supplemented to the plating solution after removing the precipitate, and the plating solution is heated to a temperature suitable for plating. After that, plating is resumed. Necessary components such as nonionic surfactants, thioureas, thiourea compounds, acids and the like can be added and these can be included in the additive together with the aromatic organic sulfonic acid to supplement the necessary ingredients.

The solid / liquid separation device may be anything capable of separating the plating liquid and the resulting precipitate; For example, filtration using a filter, sedimentation, centrifugation, or the like can be used. Here, the addition of the additive containing aromatic organic sulfonic acid is preferably performed on the plating liquid deteriorated due to the plating action, that is, the plating liquid whose performance of the plating bath is degraded in the plating process, so that the article is made of metal ions such as copper, Plated by elution of ions such as nickel, zinc, chromium, molybdenum and tungsten. As described above, the plating film is formed by forming a general plating bath and controlling the temperature within a range of 50 to 75 ° C., and then immersing the article to be plated having a metal such as copper or a copper alloy on the surface in a plating solution for 20 to 300 seconds. . In the plating process, copper ions are eluted into the plating liquid: therefore, the addition of additives containing aromatic organic sulfonic acids, cooling of the plating liquid, recycling of the plating liquid, and capturing and removing precipitates can be carried out in the required order in the required order.

The fourth method of the present invention is a main tank for performing electroless tin plating, a settling tank in which a precipitate is formed, a recirculation pipe connecting the main tank and the settling tank so that the electroless plating solution can be recycled, and the settling tank and the main tank A method of performing electroless plating on an article to be plated using a plurality of tank plating apparatuses using a solid plating solution interposed therebetween and using a tin plating solution containing a nonionic surfactant and a thiourea or thiourea compound. to be; This method comprises (A) adding an additive containing an aromatic organic sulfonic acid or a salt thereof to the plating liquid in the precipitation tank; (B) cool the plating liquid; (C) capturing the precipitate produced by cooling using a solid / liquid separation device, which steps (A), (B), (C) or (B), (A), (C) It is done in order.

The fourth method of the present invention is characterized by using a plurality of tank apparatuses provided with a settling tank which forms a precipitate as well as a main tank to which electroless plating is performed. At least two tanks are required, but three or more tanks can also be used if necessary. The main tank and the settling tank used may have the desired size and shape as long as the respective plating treatment and the precipitation formation can be carried out. The thermostat is preferably installed in the main tank and in the settling tank; Heating is preferentially carried out in the main tank and cooling is preferentially carried out in the settling tank. The main tank and the settling tank are piped to allow the electroless plating solution to circulate between the two tanks. The pipe may be of any kind as long as the plating liquid can be circulated. In addition, the solid / liquid separation apparatus may be installed in a path through which the plating liquid flows from the precipitation tank to the main tank and separates the precipitate formed by adding and cooling an additive containing aromatic organic sulfonic acid. Steps (A)-(C) may be performed in the order of (A), (B), (C) or (B), (A), (C).

In one of these sequences, the precipitate is formed in the settling tank, but plating continues in the main tank; This has the advantage that there is no need to stop the plating operation. The temperature of the plating liquid in the main tank is preferably 50-75 ° C, and the temperature of the plating liquid of the plating tank is preferably in the range of 5-30 ° C. Capture the precipitate prepared in the step (A) adding an additive containing an aromatic organic sulfonic acid or salt thereof to the plating liquid, (B) cooling the plating liquid and (C) capturing the precipitate using a solid / liquid separation device. The method is as described above.

The fifth method of the present invention provides a plating tank for storing a plating liquid and performing electroless tin plating, a recycling pipe connected to the plating tank in a manner capable of recycling part or all of the plating liquid, and solids installed in a recycling path of the plating liquid. A liquid separation device, and a thermostat for cooling or heating the plating liquid in the plating tank, and also being plated using a single tank plating device, using a tin plating liquid containing a nonionic surfactant and a thiourea or thiourea compound. A method of performing electroless tin plating on an article; This method involves (A) immersing the article to be plated in a plating solution in a plating tank, (B) adding an additive containing an aromatic organic sulfonic acid or a salt thereof to the plating solution and cooling to produce a precipitate, (C) the resulting precipitate Removing from the plating liquid using the solid / liquid separation device.

The fifth method of the present invention is characterized by using a single tank apparatus, wherein the single tank plating apparatus is used to form an precipitate by adding an additive containing an aromatic organic sulfonic acid to a plating tank in which electroless plating is performed. Used. The plating tank used can be of any size and shape as long as it can perform plating treatment and precipitation formation. The thermostat can be in any form as long as the plating liquid can be adjusted to the desired temperature. As described above, circulation pipes and solid / liquid separation devices can be used in the desired form.

In step (A), the article to be plated is immersed in the plating solution of the plating tank and displacement plating is performed. The plating liquid temperature in the plating tank is preferably 50-75 ° C. As the substitution plating proceeds in the plating tank, the copper ions eluted from the article to be plated accumulate in the plating liquid. In step (B), an additive containing aromatic organic sulfonic acid is added to the plating liquid in the plating tank. The addition method is as above. Further, in step (B), the plating liquid in the plating tank to which the additive containing aromatic organic sulfonic acid is added is cooled. Cooling may be carried out before or after adding the additive containing the aromatic organic sulfonic acid. The temperature of the plating liquid upon cooling is preferably in the range of 5-30 ° C. as above. The plating operation will be stopped because the plating temperature is below the range suitable for plating during step (B). In step (C), the precipitate produced in the plating tank is sent to the solid / liquid separation device through the circulation pipe to be separated and removed from the plating liquid. Recycling of the plating liquid will be performed after step (B) is finished.

The sixth method of the present invention is a method for managing an electroless tin plating solution containing a nonionic surfactant and a thiourea or thiourea compound and used for electroless tin plating of copper or copper alloys; In the plating liquid management method, the copper ion concentration in the plating liquid is reduced by adding an additive containing an aromatic organic sulfonic acid or a salt thereof to the plating liquid and cooling to produce a precipitate.

In all the above types of plating tanks, the copper concentration in the plating liquid is measured, and the additive containing aromatic organic sulfonic acid is added to the plating liquid at a suitable time before the copper concentration reaches an upper limit that adversely affects the plating, and then the aromatic organic The plating liquid to which the additive containing sulfonic acid is added is cooled, and a precipitate is formed to reduce the copper ion concentration in the plating liquid and to adjust the electroless plating liquid to an optimum state. The measurement of copper ions in the plating liquid can be carried out in a preferred manner, for example, the copper ion concentration can be measured by atomic absorption or ICP by sampling a portion of the plating liquid.

Example

Examples 1-5

Electroless plating solutions were prepared with the following composition:

Tin fluoroborate (as Sn ²⁺ ): 37 g / L

Methanesulfonic acid: 50 g / L

Hypophosphate: 30 g / L

Thiosulfate: 100 g / L

Nonionic surfactant of Table 1: 50 g / L

20 g / L of copper powder was added to each of the tin plating solutions and heated at 65 ° C. for 5 hours with stirring. When the substitution reaction of copper and tin was completed, an electroless tin plating solution containing copper ions deteriorated was prepared. Maintaining the simulated deteriorated plating solution at 65 ° C; 70 g / L paratoluenesulfonic acid was added as an additive and the plating liquid was cooled to 25 ° C. After cooling the plating solution, free material was produced in the plating liquid. The free material was removed by passing the plating solution through a filter (0.2 micron), filtered and the copper concentration in the plating solution was measured by atomic absorption. The results are shown in Table 2.

Example 6

Benzenesulfonic acid was used instead of the paratoluenesulfonic acid of Example 4; Benzenesulphonic acid was added as a additive to the simulated deteriorating liquid containing copper ions maintained at 65 ° C. in the same manner as in Example 4, and then the plating liquid was cooled to 25 ° C. After cooling the plating solution, free material was produced in the plating liquid. The resulting free material was caused by precipitation and the supernatant was sampled to measure the copper concentration in the plating solution by atomic absorption. The measured copper concentration was 0.4 g / L.

Example 7

A simulated deteriorated electroless tin plating solution containing copper ions was prepared in the same manner as in Example 3. The simulated deteriorated plating solution was cooled to 30 ° C. At this time, no free material was produced. The simulated deteriorated plating solution was maintained at 30 ° C. and 70 g / L paratoluenesulfonic acid was added. Immediately after addition, free material was produced in the plating liquid. The plating solution was passed through a filter (0.2 micron) to remove free material and the copper concentration in the plating solution after filtration was measured by atomic absorption. The measured copper concentration was 0.9 g / L.

Comparative Example 1

The same procedure as in Example 1 was conducted except that no nonionic surfactant was used, and the copper concentration in the plating solution after filtration was measured by atomic absorption. The results are shown in Table 3.

When no nonionic surfactant was used, the copper removal rate was much worse than that of Examples 1-7, and it was confirmed that the aromatic organic sulfonic acid was not consumed.

Comparative Example 2

Except for using isethionic acid (isethionic acid) instead of paratoluenesulfonic acid was carried out in the same manner as in Example 2, the copper concentration in the plating solution after filtration was measured by atomic absorption. The measured copper ion concentration was 7.2 g / L.

Comparative Example 3

The same procedure as in Example 2 was carried out, except that isethionic acid was used instead of paratoluenesulfonic acid and no nonionic surfactant was used. The concentration of copper in the plating solution after filtration was measured by atomic absorption. . The measured copper ion concentration was 7.4 g / L.

Example 8

An impurity repeated removal test and a test for evaluating plating performance after removing impurities were performed. Using a plating liquid similar to that of Example 4, electroless tin plating was performed under the following conditions. Copper was added in the same manner as in Example 4 to prepare a simulated deteriorated plating solution, and electroless tin plating was performed with this simulated deteriorated plating solution. Thereafter, paratoluenesulfonic acid was added as in Example 1, and impurities were filtered after plating. Further spent thiourea, nonionic surfactant (polyoxyethylene β-naphthyl ether), tin fluoroborate and the like were added to the plating liquid after filtration and the concentration was adjusted to the same concentration as in the plating liquid before the addition of copper. This method was performed four times in total.

The results are shown in Table 4.

Plating conditions: temperature 65 ℃; Plating time 195 seconds

Claims (6)

Adding an aromatic organic sulfonic acid, a hydrate thereof, or a salt thereof to an electroless tin plating solution comprising a nonionic surfactant and a thiourea or a thiourea compound, followed by cooling to form a precipitate of impurities; Removing the precipitation of impurities from the electroless tin plating solution. The method of claim 1, further comprising contacting the copper or copper alloy with an electroless tin plating solution to plate tin on the copper or copper alloy. The method of claim 1 wherein the precipitation of impurities is removed by a solid / liquid separation device. The method of claim 1 wherein the amount of aromatic organic sulfonic acid or salt thereof is from 5 to 200 g / L. The process of claim 1 wherein the aromatic organic acid is selected from phenolsulfonic acid, benzenesulfonic acid, toluenesulfonic acid and naphthalenesulfonic acid. The method of claim 1 wherein the precipitation of impurities comprises one or more of copper, nickel, zinc, chromium, molybdenum and tungsten ions.