JPH01268894A - Tin, lead or tin/lead alloy electrolyte for high speed electroplating and method - Google Patents

Abstract

PURPOSE: To obtain a plated article having matting and good solderability, by using an electrolyte consisting of a main soln. consisting of alkylol sulfonic acid, etc., a soln. of tin and/or lead compd. and a prescribed surfactant.

CONSTITUTION: The electrolyte of the compsn. consisting of alkyl or alkylol sulfonic acid, the soln. of tin and/or lead compd. and a surfactant is prepd. The surfactant is formed out of ≤20C org. compd. having a hydroxyl group condensed with an alkylene oxide compd. or its soln.-soluble deriv. The electrolyte is maintained at foamless, colorless and non-turbid, stable state under electroplating conditions of a high speed by this surfactant. The smooth surface having a pale gray satin finish and good solderability is yielded.

COPYRIGHT: (C)1989,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrolytic solution based on low alkyl or low alkylol sulfonic acids or derivatives thereof, used for high speed electroplating of tin, lead or tin/lead alloys. In particular, the present invention relates to the electrolytic solution used in a high-speed electroplating apparatus and an electroplating method using the same.

[Conventional technology]

Electrolytic baths for depositing tin, button, and their alloys have been used in electroplating equipment for many years.

Also, high speed electroplating equipment and high speed plating methods are well known in the industry and generally.

The article to be plated is introduced from one end of the plating tank.

It consists of advancing through the plating tank and then taking it out from the other end of the plating tank. The electroplating solution overflows the electroplating tank into a reservoir and is pumped back from the reservoir to the electroplating tank to provide vigorous agitation and circulation. There are many variations of these electroplating baths, but the general highlights are as described above.

There are a number of key points that the electroplating solution should have in order to achieve good performance in this type of apparatus and method, including:

1. The solution must be capable of electroplating the desired alloy deposits at the high rates required.

2. The deposit must be shiny and fine-grained even at the high current densities required for high speed plating.

3. The deposit must have good solderability and be capable of meeting the required solderability specified for such deposit.

4. The solution must be stable and the additives resistant to exposure to strong acid solutions and to the introduction of air that results in vigorous solution movement in high-speed plating equipment. Must.

5. The solution must remain transparent and turbid at elevated temperatures of approximately 49°C to 54°C (120 to 130@F) or higher, due to the high current density and small volume of the solution. Therefore.

These solutions (baths) tend to heat up in high speed plating baths until they reach equilibrium at high temperatures. The additive must be of a type that does not cloud the solution at such high temperatures.

6. Due to violent solution movement and mixing with air, there is a high possibility of bubble generation which is harmful to the electroplating process.
Under extreme conditions, air bubbles may form within the reservoir with the resulting overflow to the floor, which may cause large amounts of solution to be lost to the waste stream. “Depth control plating” (“C0n-trolle
d depth plating"), the part to be plated is partially immersed so that part of the article is below the surface of the solution. In this case, the unplated part of the article is separated from the plated part. It is desirable to have a clear and similar boundary line.If the solution produces bubbles, such bubbles will prevent the formation of a good boundary line.Bubbles may also cause agitation. The presence of air bubbles can also cause electrical discharge between the anode and cathode. Because of these problems, the additives used are It must not generate bubbles.

A number of electrolytes have been proposed for electroplating tin, lead and tin/lead alloys, one of which is described in U.S. Pat. No. 4,701,244.

This patent discloses the electroplating of tin, lead or tin/lead alloys from low alkyl sulfonic acid baths containing brightening additives and various types of wetting agents. Surfactants that have been proposed as useful include betaines, alkylene oxide polymers, imidazole compounds, quaternary ammonium compounds, ethylene oxide derivatives of amines, m-acid salts, amines, and the like.

U.S. Pat. No. 4,622,999 discloses an electroplating bath for electrowelding of tin, lead or tin/lead alloys from an alkane or alkanol sulfonic acid bath containing surfactants and other additives. be. In this patent, surfactants are shown to be nonionic, cationic, anionic or amphoteric. A large number of examples are given for various types of surfactants, and a large number of various types of wetting agents are listed that can be used.

Also, US Pat. No. 4,673,470 describes tin, lead or tin/lead alloy plating baths based on aliphatic or aromatic sulfocarboxylic acids. Instead of the alkane or alkanol sulfonic acids disclosed in earlier patents, this patent includes carboxylic acid groups in the organic sulfonic acid compounds. The electroplating bath described here contains brighteners and surfactants (
Particular emphasis is placed on nonionic surfactants). A very wide range of surfactants have been described as useful, and many different wetting agents have been listed.

In all of the proposed prior art baths, the wetting agents that are stated to be effective in providing a glossy or matte deposit surface are described very extensively and are considered equivalent to each other. In each of these prior art patents, numerous examples are given for a variety of drugs of many different types, the majority of which involve some type of oxide or similar condensation compound.

[Problem to be solved by the invention]

However, most of the prior art wetting agents are unsuitable for high speed plating in modern high speed plating equipment. These wetting agents fail to satisfy some or all of the requirements that the electrolyte should have as described above. It is an object of the present invention to overcome the problems of the prior art by providing particularly preferred agents useful in high-speed electroplating equipment and methods.

[Means to solve the problem]

The present invention relates to an electrolytic solution used for depositing tin, lead or a tin/lead alloy on a substrate by high-speed electroplating, and comprising the following components:

That is, a main solution consisting of an alkyl or alkylol sulfonic acid, at least one of which is a solution soluble in a tin compound or a lead compound, and a solution containing 1 or more carbon atoms.
An aliphatic hydrocarbon consisting of 7, preferably 6 or less, having at least one hydroxyl group, but containing a surfactant consisting of an alkylene oxide condensation compound or a solution-soluble derivative thereof, preferably an interfacial The activator imparts a cloud point to the solution of about 110 degrees Fahrenheit or higher, and the electrolyte preferably includes a brightening agent if a shiny deposition surface is desired.

A preferred hydrocarbon is an alcohol such as butyl alcohol. Also, to achieve the desired cloud point,
Alkylene oxide compounds.

Preferably, 4 to 40 moles, preferably 6 to 28 moles, of ethylene oxide are used to form the condensation compound. Several moles of ethylene oxide may be substituted with propylene oxide.

Other suitable surfactants are alkylene oxide condensation compounds of aromatic organic compounds having 20 or less carbon atoms or solution-soluble derivatives thereof. This aromatic compound preferably contains one or two rings, and when one having two rings is used, it preferably contains 10 to 12 carbon atoms. Further, the aromatic organic compound preferably has an alkyl moiety having 6 or less carbon atoms, and preferably has one or more hydroxyl groups. The aromatic compound is preferably benzene, naphthalene, phenol, toluene, bisphenol A, styrenated phenol, or an alkylated derivative thereof.

Accordingly, a desirable surfactant is an organic compound having up to 20 carbon atoms fused with a sufficient amount of an alkylene oxide compound or a solution-soluble derivative thereof to form a solution containing about 4
Includes those that provide a cloud point of 3°C (110°F) or higher.

The invention also includes methods and processes for high speed electroplating of tin, lead or tin/lead alloys. The method uses high speed electroplating equipment of the type described above. The equipment includes an electroplating tank, an overflow storage tank adjacent to the tank, a pump for returning the solution from the storage tank to the plating tank via one or more distribution pipes, and a pump for transporting the substrates to be plated from an input port at one end of the tank to the plating tank. and a means for conveying it to an outlet at the end. Further, the electrolytic solution of the present invention is introduced into the apparatus so that the plating tank is sufficiently filled with the electrolytic solution.

Also, the electrolyte continuously overflows into the reservoir and is continuously returned to the plating bath so that vigorous agitation and circulation of the electrolyte occurs within the plating bath.

In this manner, the substrate is continuously electroplated during its passage through the plating bath.

[Effect]

Herein, tin, lead or tin/lead alloy electroplating is suitable for high speed electroplating operations using modern high speed electroplating equipment and specifically designed to deposit satisfactory matte or bright deposits. The plating composition will be described. There is a limited number of wetting agents that meet all of the foregoing requirements for obtaining satisfactory high speed electroplating. These compounds are ethylene oxide derivatives (low molecular weight) of aliphatic alcohols containing alkyl groups with up to 8 carbon atoms or ethylene oxide derivatives of aromatic alcohols containing up to two aromatic rings (here, aromatic rings may be substituted with an alkyl group having up to 6 carbon atoms, or may be substituted with a bis compound having an alkyl group having up to 6 carbon atoms). be. In addition, here, the aromatic compound has 2 carbon atoms in the state before condensation with the alkylene oxide compound, regardless of whether it is alkylated or not.
Must not contain 0 or more.

Sulfonic acids suitable for the present invention include alkyl or alkylol sulfonic acids having up to 5 carbon atoms. Alkanesulfonic acids, especially methanesulfonic acid, are preferred. These acids account for 10-30% of the electrolyte by volume.
amount, and thus free acid is present. In this way, the pH of the electrolyte becomes 2 or less, usually 0.5 or less.

Surfactants suitable for the present invention meet all of the above requirements, i.e. the deposit has good solderability and has a matte or glossy finish with sufficient particle definition. The solution must be stable in acid baths, capable of high-speed electroplating, have a JA temperature of approximately 43°C (approximately 110'F) or higher, and contain almost no air bubbles during electroplating operations. It's like being satisfied with that.

Foaming properties are measured in the laboratory by using typical base solutions used in high speed electroplating. The composition of the solution is as follows.

Metallic tin (as tin methanesulfonate) 2
0g/Q methanesulfonic acid
Surfactant to be tested at 15% volume ratio
Volume Ratio 1% Temperature Ambient temperature to about 24°C (~75°F) The relative degree to which the surfactant forms bubbles in the base solution is tested by placing solution 100IIQ in a graduated 250m f2 cylinder. .

Air is supplied by a commercially available laboratory or fish tank aerator and is directed through a disperser to the bottom of the solution in the graduated cylinder. The following two methods are preferred as test methods. One method is to set the air supply time to 2 minutes and measure whether the height of the bubble surface exceeds 15011Q or the top surface of a graduated cylinder. In this case, if the bubble surface exceeds 150 mQ or exceeds the top surface of the cylinder, the surfactant is judged to be unsuitable and no further tests are conducted. The second method is bubbling air into the fresh solution for 10 seconds.
At the end of the 10 seconds, read the maximum foaming surface height on the scale cylinder and record the time until the bubbles have completely dissipated and returned to the original 100mm scale. do. For a surfactant to pass this test, the maximum foaming surface height must not exceed 150 tan and the time required for bubble dissipation must not exceed 20 seconds.

Cloud point is measured by taking a solution containing 1% surfactant and gradually increasing the temperature until the solution begins to become cloudy. A cloud point of about 49° C. (about 120° F.) or higher is considered fully satisfactory, and a cloud point of about 43° C. (110° F.) or less is considered unsatisfactory.

The base solution used in the high speed electroplating apparatus and method of the present invention generally contains relatively high concentrations of metal and acid. The inclusion of such high concentrations of metals and acids will affect the cloud point of the electrolyte. For example, a surfactant that gives a high cloud point in a dilute electrolyte will have a low cloud point in a highly concentrated electrolyte such as those mentioned above. Gives a cloud point. Therefore, it is important to measure the cloud point of all electrolytes intended to obtain the desired deposition surface.

The high-speed electroplating properties of the solution and the particle definition of the deposition surface are
Measurements are made using a Hull cell operating at approximately 43° C. (120@F), a total current of 5 amps, and stirring with a paddle stirrer. In this case, the solution has the following composition.

Metallic tin (as tin methanesulfonate) 1
0g/Q total amount of methanesulfonic acid
30% surfactant by volume (if necessary)
1~10m12/Q Under these conditions, the Hull Cell panel shows a deposited surface of 1/4' or more without discoloration in the high current density region, and the deposited surface in the remaining part is matte or slightly glossy. , shall exhibit a smooth light gray finish.

The stability of the surfactant-containing electrolyte is determined by electroplating the bath for at least 20 amp hours per liter. The properties of the electroplating solution and its deposition surface must not be affected by electroplating.

The solderability of the deposited surface is measured according to the method given in Mil-5td 202F, Method 208F (April 1986 Edition). The deposited surface must pass the tests given in the above military standards.

The surfactants included in this invention all have high cloud points,
It contains a sufficient amount of a hydrophobic organic compound condensed with alkylene oxide, preferably ethylene oxide, to satisfy stability, high current density and particle definition. Propylene oxide may be included together with ethylene oxide. However, the amount of propylene oxide used and its ratio to ethylene oxide must be such that the cloud point is sufficient to pass the above conditions. Propylene oxide can be used to reduce the foaming properties of surfactants. However, only limited amounts of propylene oxide can be used because it lowers the cloud point of the resulting electrolyte. A person skilled in the art can readily determine the amount of propylene by routine experimentation.

The organic compound may be any aliphatic hydrocarbon (saturated or unsaturated) having 8 or less carbon atoms and containing at least one hydroxyl group. Similarly, organic compounds are aromatic ring compounds such as benzene, naphthalene, phenol, toluene, bisphenol A, and styrenated phenols that do not contain more than one ring and have a substituted alkyl chain of 6 or fewer carbon atoms. Good 6 again. The ring may be substituted with one or more hydroxyl groups.

To illustrate a particular compound, octylphenol ethoxylate with 12 moles of ethylene oxide is unsuitable for the practice of this invention. This is because the alkyl chain has a long length, resulting in extremely high foaming properties. Beta naphthol with 13 moles of ethylene oxide is suitable for the practice of the present invention and can pass all of the above requirements. Styrenated phenols with more than 2 moles of styrene condensed with 12 moles of ethylene oxide are unsuitable because they have 3 aromatic rings. 5-ethyloxylated bisphenols A are suitable and meet the above requirements. Satisfy everything. This compound has two aromatic rings and three alkyl carbon atoms.

Other surfactants suitable for the practice of this invention include ethyloxylated butyl alcohol (with or without propylene oxide). The longer the chain length of the aliphatic alcohol, the higher the foaming properties. The foaming properties of this group of compounds can be reduced considerably by including some propylene oxide in the molecule. However, the above propylene oxide content needs to be sufficiently controlled to prevent the cloud point from decreasing, resulting in a cloud point of approximately 43°C (110°C).
F) is inappropriate. For this series,
The maximum chain length of the alkyl group must be 8 or less carbon atoms.

In the present invention, the electroplating bath contains solution-soluble tin and/or lead metals (preferably as alkyl sulfonates or alkanol sulfonates) and some additives or free alkanes or alkanesulfonic acids. do. One surfactant suitable for the practice of this invention has already been mentioned in order to provide a suitable matte or semi-glossy deposit. However, it is possible to improve the glossiness of the deposit by adding known brighteners, such as those disclosed in the prior art cited above. The resulting electroplating bath will have all of the desirable properties of a bright or semi-bright deposit.

Surfactants can further increase solution solubility by techniques well known in the art. Solution-soluble derivatives of the desired surfactants can be obtained by sulfation, sulfonation, phosphorylation, phosphorylation, carboxylation, and the like. However, in this case, the derivative must not impair the suitability of the material for the purposes of the invention already mentioned.Today, various high-speed electroplating devices are available on the market. One typical device is disclosed in U.S. Pat. "High-speed electroplating line with insoluble anode"("High 5
pead Electrogalvanizing L
ine with In5olable An.

de at K1l1itsu Works of N
1ppon 5teal Corporation”)
, J.J. Miles
) “Floating plating as a continuous process” by others (Pa5w
1m Plating as a Continue
s Process”), Etch Wettoner (H,
"Continuous plating of copper, nickel and chrome on wide steel sheets for decorative and functional purposes" by
(“Continuous Plating of C
opper, N1ckel and Chromiu
m on WideSteel 5trip for
Decorative and Function A
A high-speed machine for depth-controlled electroplating is described in "How to Save Gold in Selective Deposition" by C.D. Eidschun. to 5 ave
Goldwith 5electj,ve Depo
"sits").

These documents were published at the American Electroplaters Association 2nd Continuous Plating Seminar, Chicago, Illinois.

January 24-26, 1977) (America
n Electroplater's 5ociety
's 5econd Continuous Plat
ing Saminar, Chicago, l1lin
ois, January 24-26, 1977). It must be emphasized here that these high speed electroplating apparatuses are given by way of example only and are within the scope of the detailed description of the invention. Those skilled in the art are aware that a wide range of similar equipment exists that are useful for high speed electroplating according to the present invention.

〔Example〕

The scope of the invention is further described with respect to the following examples, which are presented merely to illustrate preferred embodiments of the invention and are not to be construed as limiting the scope of the invention in any way.

Three stock solutions were used on each side to test the ability of each surfactant to electroplate pure tin, 90/10 tin/lead alloy, and 60/40 tin/lead alloy. The compositions of these solutions are as follows.

Pure tin A piece Lu V-tempered metal tin g/l 72 72 40
Metallic lead (as tin methane sulfonate)
g/1-18 26 (as lead methane sulfonate) Methane sulfonic acid 15 15 15 (
Volume X) The surfactant on each side was added in increments until the optimum amount was reached. Testing of solution and electroplated deposited surfaces was performed using all of the test methods listed above.

1) Foaming 2) Cloud point of the solution 3) Crystal graining (smooth, light gray satin finish) 4) Speed of electroplating 5) Solderability of the deposit 6) Stability of the solution Each of these example solutions showed a pH of 0.5 or less.

■-Bisphenol A with 8 moles of ethylene oxide
6 to 12 ml/1 was used. The solution with this surfactant passed all six tests.

The same amount of bisphenol A with 10 moles of ethylene oxide as in Example 1 was also used. Solutions with this surfactant also passed all tests.

3 to 6 ml of bisphenol A sulfate with 30 moles of ethylene oxide per unit was used. Solutions with this surfactant also passed all tests.

0.5-1 ml of beta-naphthol containing 13 moles of ethylene oxide was used. Solutions with this surfactant also passed all tests.

(2)-Dan (comparison) 3 to 6111 polystyrenated phenols having 12 moles of ethylene oxide were used. This surfactant formed numerous bubbles and, although it passed the other tests, did not provide a satisfactory deposition surface.

Comparison: 3-8 ml of octyl alcohol with 12 moles of ethylene oxide were used. This surfactant is unsuitable because it foams too much.

Iku (comparison) Butyl alcohol with 5 moles of ethylene oxide was used from 2 to 8 companies. Other tests passed despite the unsatisfactory grain definition of the plated surface. Thus, the number of moles of ethylene oxide must be increased to at least 6 or more, as shown in Examples 8 and 9. 1~4 o+
1 was used. Solutions with this surfactant passed all tests.

Body: - Butyl alcohol containing 8 moles of ethylene oxide and 6 moles of propylene oxide is added to
Use lml. Solutions with this surfactant passed all tests.

A bright plating was obtained by adding a well-known brightener such as an aromatic aldehyde such as 5-1-chlorobenzaldehyde or its derivatives, e.g. benzal acetone, to the above solution which passed all tests.

While the invention disclosed herein is clearly well calculated to meet the above objectives, many modifications may be devised by those skilled in the art, and the scope of the additional claims may reflect the claimed invention. It is intended to cover modifications and embodiments as may fall within the original spirit and scope.

Claims (1)

[Claims] 1. An electrolytic solution used for depositing tin, lead or a tin/lead alloy on a substrate by high-speed electroplating, consisting of the following components: A main solution consisting of an alkyl or alkylol sulfonic acid; at least One of the solutions is a tin compound-soluble or lead compound-soluble solution; consisting of an organic compound having at least one hydroxyl group and having 20 or less carbon atoms condensed with a sufficient amount of an alkylene oxide compound or its solution-soluble derivative. A surfactant that keeps the electrolyte essentially bubble-free, clear and stable under high-speed electroplating conditions, resulting in a light gray satin finish and good solderability. It is possible to provide a smooth electroplated surface with properties, and the organic compound has 1 carbon atom.
Contains one of aliphatic hydrocarbons, aromatic compounds, or alkylated aromatic compounds in the range of ~7. 2. The electrolytic solution according to claim 1, wherein the organic compound is an aliphatic hydrocarbon having 6 or less carbon atoms. 3. Claim 1, wherein the organic compound is an aromatic compound having a total number of carbon atoms ranging from 6 to 12 and having one or two rings. electrolyte. 4. The electrolytic solution according to claim 1, wherein the organic compound is benzene, naphthalene, phenol, toluene, bisphenol A, or styrenated phenol. 5. The electrolytic solution according to claim 3 or 4, wherein the aromatic compound contains an alkyl moiety having 8 or less carbon atoms. 6. The electrolytic solution of claim 3 or 4, wherein the surfactant provides the solution with a cloud point of greater than about 110 degrees Fahrenheit. 7. Claim 1 characterized by containing a brightening agent
Electrolyte as described in section. 8. The electrolytic solution according to claim 1, wherein the alkylene oxide compound is ethylene oxide, and 4 to 40 moles of oxide are used to form the condensation compound. 9. The electrolytic solution according to claim 8, wherein several moles of the ethylene oxide are replaced with propylene oxide. 10. The electrolytic solution according to claim 1, wherein the solution-soluble derivative is obtained by sulfating, sulfonating, phosphate treating, phosphonately converting, or carboxylating a condensed compound. 11. A method for high-speed electroplating of tin, lead or tin/lead alloys, characterized by comprising the following steps: an electroplating cell, an overflow storage tank adjacent to the cell, and for returning the solution from the storage tank to the cell. and means for conveying the substrate to be plated from an input point at one end of the cell to an exit point at the other end of the cell; 20 carbon atoms having at least one hydroxyl group condensed with a solution, at least one of which is tin compound soluble or lead compound soluble, and a sufficient amount of an alkylene oxide compound or a solution soluble derivative thereof; A surfactant consisting of the following organic compounds that keeps the electrolyte essentially bubble-free, clear, and cloud-free under high-speed electroplating conditions, resulting in a light gray satin finish and good solderability. an aliphatic hydrocarbon which can provide a smooth electroplated surface with adhesion properties, and in which the organic compound has a carbon number of 1 to 7;
an electrolytic solution comprising an aromatic compound or a surfactant containing one of the alkylated aromatic compounds is placed in the apparatus, the electrolytic solution sufficiently filling the cell and continuously overflowing into the reservoir; The substrate is continuously introduced back into the cell so as to obtain vigorous agitation and circulation within the cell; the substrate is passed through the electrolyte in the cell to contain tin, lead or tin/lead. Continuously electroplating the alloy. 12. The electroplating method according to claim 11, wherein the means for returning the electrolytic solution to the cell comprises a pump. 13. The electroplating method of claim 11, wherein the means for returning the electrolyte to the cell comprises one or more dispersion pipes in the cell downstream of the pump. 14. The electroplating method according to claim 11, wherein the aromatic compound contains 6 to 12 carbon atoms. 15. Claim 14, wherein the aromatic compound is benzene, naphthalene, phenol, toluene, bisphenol A, styrenated phenol, or an alkylated derivative thereof having an alkyl moiety having 6 or less carbon atoms. Electrolyte as described in section. 16. The solubility of the surfactant in the electrolytic solution is increased by sulfation, sulfonation, phosphate treatment, sulfonation, or carboxylation of the condensation compound, according to claim 11. Electroplating method. 17. The electroplating method according to claim 11, wherein the alkylene oxide is ethylene oxide, in which 4 to 40 moles of oxide are used to form the condensation compound. 18. The electroplating method according to claim 17, wherein several moles of the ethylene oxide are replaced with propylene oxide. 19. The above surfactant is in solution at about 43°C (110°F).
12. The electroplating method according to claim 11, wherein the electroplating method provides a cloud point equal to or higher than the above. 20. The electroplating method according to claim 11, characterized in that a brightener is added.