Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/30—Electroplating: Baths therefor from solutions of tin
  • C25D3/32—Electroplating: Baths therefor from solutions of tin characterised by the organic bath constituents used
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
  • C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
  • C07D307/34—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
  • C07D307/38—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with substituted hydrocarbon radicals attached to ring carbon atoms
  • C07D307/40—Radicals substituted by oxygen atoms
  • C07D307/46—Doubly bound oxygen atoms, or two oxygen atoms singly bound to the same carbon atom

Definitions

• Grindle ABSTRACT Improved baths or solutions are provided for the electroplating of tin, and containing as the primary brightener therefor the reaction product of furfural with crotonaldehyde in the presence of a catalytic amount of an alkali.
• this invention is concerned with brightening additive compositions for tin-electroplating baths, and with methods for preparing such additive compositions and for electroplating bright tin deposits.
• this invention relates to electrolytic tin plating. More particularly, this invention relates to new and improved baths and methods for electroplating of bright acid tin deposits, to brightening additive compositions for tin-electroplating baths and to methods for the preparation of such additive compositions.
• Bright acid tin deposits are being used increasingly for such applications as printed circuits for the various components of devices used in the electronics industry, parts used to establish electrical contacts, and for such purposes as tools and implements for handling packaging in the food products industry.
• the deposits be bright because such bright deposits provide added protection to the circuits for later handling in that they protect the circuits much better from finger staining.
• the bright deposits for reasons which are not completely understood, solder easier in later handling and/or connection of the circuits when they are incorporated into various devices being used.
• ln plating bright tin different well-known procedures may be utilized including rack plating in which items to be plated are suspended on insulated fixtures (or racks), and barrel plating.
• rack plating a single item may be plated or a plurality of that item, or there may be different parts to be plated of a variety of sizes and configurations. Further, parts may be bulk plated, in which generally smaller parts, usually all the same and which lend themselves to a tumbling action, are disposed in a rotating barrel.
• the bath be formulated in a manner to provide the widest possible bright plate current density range. Furthermore, it is important that the limiting current density (the current density at which the deposit ceases to be sound in structure and appearance) be as high as possible to allow for the wide variations in cathode current density which may be encountered due to the size and shape complexity of the parts being plated.
• the primary brightener of this invention cooperates with known materials of the prior art, such as secondary brighteners, and wetting agents, as well known, which improve brightness and/or widen the effective operating bright plate cathode current density range in which the desired brightness for the deposits is obtained.
• known materials of the prior art such as secondary brighteners, and wetting agents, as well known, which improve brightness and/or widen the effective operating bright plate cathode current density range in which the desired brightness for the deposits is obtained.
• a further feature of this invention provides a method for bright tin electroplating in which an otherwise conventional acid tin-electroplating bath is utilized incorporating the primary brightener in accordance herewith simultaneously with application of a current interruption procedure in which current is applied with the periodic momentary interruption thereof. This is carried out in a specific predetermined cycle to provide deposits of even greater continuity and luster than is achieved with the new primary brightener'here utilizing the usual steady current application procedures.
• the cooperating additives which may be employed in cooperation with the primary brightener, in accordance herewith, may include nonionic-alkoxylated wetting agents, and formaldehyde as the secondary brightener, as well known.
• the wetting agent serves to transform the loosely adherent, spotty, sometimes dendritically crystalline tin deposit from an additive-free bath into a dense, continuous, adherent, microcrystalline deposit.
• Formaldehyde acts as a cathode depolarizer when used in cooperation with the wetting agent and other additives in the bath to help increase cathode current efficiency.
• formaldehyde is used only with the wetting agent, and in the absence of the primary brightener in accordance with this invention, an unsatisfactory deposit is obtained.
• compositions and methods herein are applicable to other barrel-and-rack electroplating processes.
• concentrations of tin and free acid may be varied generally within the limits conventional in this art. For example, a tin content of 10 to g./l. and a free acid concentration of 20 to 200 g./l.
• Sulfuric, fluoboric and aromatic sulfonic acids may be present simultaneously in the electrolytes in a manner not novel in itself.
• antioxidants used in acid tin-plating solutions may be utilized when employed in the tin-plating solutions of the invention in small amounts.
• the temperature of the plating solution is generally ambient, and preferably held below 35 C. and within the range of between about l20 C. for optimum plating performance.
• Stannous sulfate (SnSOn 30 g./l. Concentrated sulfuric acid (8.0. 1.84) lOS ml./l. Primary brightener 0.25 g./l. Carrier 4 g./l. Secondary brightener l0 ml./l.
• the secondary brightener is preferably formaldehyde in a 37 percent solution.
• the carrier may be any well-known nonionic-alkoxylated wetting agent, such as, for example, Tergitol Nonlonic NP-35, a product of Union Carbide and being a polyethoxylated nonyl phenol having an average of oxyethylene groups.
• the wetting agent is generally added as an aqueous stock solution in the amount of 400 g./l., and added to the bath at a concentration of 40 ml./l., or 4 percent by volume.
• the primary brightener generally is added in the form of a stock solution in an organic solvent such as, for example, Cellosolve, ethylene glycol monoethyl ether, in the amount of preferably g./l.
• the stock solution is added to the bath at a concentration of 10 ml./l., or 1 percent by volume.
• the periodic current interruption cycle may be used both for rack-and-barrel plating, it is of particular advantage for rack plating because in rack plating generally only moving cathode rod-type agitation can be used, which does not always provide sufficient agitation to maintain proper concentration of brightening additives, especially adjacent the cathode surface.
• reaction temperature is generally maintained within the range of between about 5 and 50 C., and preferably between about 0 and 25 C. Although effective results have been achieved in the higher operating ranges, and even up to the maximum of 50 C., it appears from subsequent use that the brightening constituents of the primary brightener herein are obtained in higher concentrations when the lower operating temperatures are utilized.
• EXAMPLE 1 41.4 ml. of furfural (0.5 mole) and 45 ml. of percent crotonaldehyde (0.5 mole) were added to 200 ml. of water. The suspension obtained was cooled with an ice-salt bath to a temperature within the range of between about 1 and +4 C. 4 grams of sodium hydroxide (0.1 mole) were dissolved in 50 ml. of water. The sodium hydroxide solution was thereafter added to the aldehyde suspension drop by drop with cooling and stirring. After the addition of the sodium hydroxide solution during which a maximum temperature of 15 C. was reached, the stirring was continued for another 2 hours. Thereafter, the solution was acidified to litmus with glacial acetic acid.
• the bottom layer of product was extracted with three 150 ml. portions of chloroform.
• the chloroform extract was then dried over anhydrous magnesium sulfate and filtered. Thereafter, the low-boiling components were removed under aspirator vacuum, keeping the bath at a temperature of between about 7080 C. 83 grams of reaction product were obtained.
• the product was a yellow brown liquid, appearing slightly viscous.
• crotonaldehyde is available from Union Carbide as crotonaldehyde 89 percent in drum quantity, and furfural is available in almost percent purity from Quaker Oats Company.
• EXAMPLE 2 205 ml. of furfural (2.5 moles), 225 ml. of 90 percent crotonaldehyde (2.5 moles) and 500 ml. of water were mixed and cooled in an ice-salt bath. When the temperature went down below 0 C., a solution of 20 grams of sodium hydroxide (0.5 mole) dissolved in ml. of water was added drop by drop with stirring and cooling. A maximum reaction temperature below 20 C. was maintained.
• the aqueous layer was extracted with chloroform and 28 grams more of a thick yellow brown liquid were obtained, to give a total combined yield of 422 grams of primary brightener.
• EXAMPLE 3 Reaction vessel: 25-gallon stainless steel container immersed in IOO-gallon plastic tank filled with crushed ice.
• the furfural, crotonaldehyde and water were stirred together and cooled to 1 C.
• the NaOH solution was added slowly to the mixture and when a total of 800 ml. had been added the temperature began to rise.
• an internal tantalum coil with 4 C. water running through it was installed and the maximum temperature rise was to 50 C. within a time of about 1 hour.
• the temperature had been reduced to about C. after about 1 hour the remainder of the NaOH solution was added and no further rise in temperature occurred.
• the mixture was then stirred for 4 hours and 1,700 ml. of glacial acetic acid were added in small increments to pH of about 6.0.
• the reaction mixture was allowed to stand overnight and the aqueous top layer was siphoned off.
• the thick remaining material was transferred into 13 polyethylene l-gallon containers. These were allowed to stand to effect further separation of water which was then decanted off. Total weight of product was about 120 pounds.
• the product is comprised of a plurality of components each of which may cooperate with the other components in order to provide the enhanced results achieved in accordance herewith.
• the exact identity and concentration of each component is not known, it can be theorized further that perhaps some of the components may be inert, or at least brightener-inactive and that some interact in a manner not known in order to provide the enhanced results obtained.
• the range of concentration of the primary brightener, in accordance herewith, contained in the bath will vary widely depending upon the results attempting to be achieved, and the various other additives and components of the bath. However, too low a content will result in a grey to dull, nonuniform, somewhat grainy deposit. On the other hand, too high a concentration level does not seem to do any particular harm although the rate of consumption of the additive may be increased, thus increasing the cost ofthe operation. Generally, it can be said that the range of primary brightener in the bath will be between about 0.1 g./l. and l g./l., with a preferred range being between about 0.2 g./l. and 0.4 g./l.
• EXAMPLE 4 Into a standard Hull Cell equipped with a magnetic stirrer to provide mild agitation there were introduced 250 ml. of an acid tin stock solution containing 30 g./l. SnSO. and ml./l. of C.P. concentrated sulfuric acid (Sp. Gr. 1.84). To the solution there were added 4 g./l. Tergitol Nonlonic NP-35. A polished brass panel was cleaned, given a 1-minute cyanide copper strike and after water rinsing, dilute acid clipping and water rinsing was immersed in the Hull Cell at a cell current of 1 ampere for 5 minutes at room temperature.
• the deposit obtained was dull white, uniform and smooth and gave good low current density coverage.
• Example 4 was repeated after adding as an additional bath component 10 ml./l. of 37 percent formaldehyde solution.
• the high current density one-third of the panel area had a nonuniform, dark, smutty deposit while the remainder of the plated area was dull white as in example 4.
• Example 5 was repeated after adding as an additional bath component 0.25 g./l. of the primary brightener of example 1 as a 25 g./l. stock solution in Cellosolve.
• the deposit obtained was uniformly lustrous throughout the entire current density range of 0 to about 6 amperes per square decimeter (ASD) and had a pronounced gloss.
• EXAMPLE 7 In this example, example 6 was repeated but as the primary brightener the product obtained from example 2 above was used as a 25 g./l. stock solution in Cellosolve. Again, the deposit obtained was uniformly lustrous throughout the entire current density range, and had a pronounced glossy appearance.
• EXAMPLE 8 In this example, example 6 was repeated but using as the primary brightener the product obtained from example 3 noted above as a 25 g./l. stock solution in Cellosolve with essentially the same results obtained.
• EXAMPLE 9 A 4-liter volume of acid tin stock solution having a concentration of 30 g./l. SnSO and 105 ml./l. of CF. concentrated sulfuric acid (SP. Gr. 1.84) was set for electrolysis at ambient temperature (about 20 C.) in a rectangular glass battery jar. In the solution there was immersed, by suspending from a titanium wire, a slab of 99.99 percent pure tin as anode. The cathode was a polished brass strip having dimensions of 20.3X2.54 l1 cm. After cleaning, it was immersed in the plating bath to a depth of 18 cm. at a distance of 10 cm. from the anode with the front of the cathode parallel to the anode. The cathode was moved in a plane parallel to the anode using a 5 cm. reciprocating stroke with a total distance travel of about 160 cm. per minute.
• Example 9 was repeated using a periodic current interruption cycle of 10 seconds plate2-seconds no-plate and using a current of 2.5 amperes for a total time of 12 minutes to give the same total plating time as for example 9.
• the resulting deposit was remarkably brighter than the one of example 9, with only a very slight milky haze.
• Example 1 l was repeated using a current of 10 amperes for minutes. The resulting deposit was uniform and brilliant and also had an average thickness of0.00064 cm.
• An aqueous acid bright tin-electroplating solution including a tin salt, free acid, and, as the primary brightener therefor, an amount sufficient to produce a bright tin electrodeposit, of a yellow brown liquid reaction product characterized as being produced by the steps which comprise placing furfural and crotonaldehyde as reactants in a reaction zone, said reactants being placed in said reaction zone in the ratio in the range between equimolar quantities and l5-percent mole excess of furfural; maintaining the temperature of the said reaction zone between about 5 and 50 C.; reacting the said reactants in the presence of a catalytic amount of an alkali to obtain a reaction product; adding an acid to said reaction product for the acidification thereof; and separating the reaction product from the acid reaction zone.
• a solution as recited in claim 3 and including a wetting agent 4.
• a solution as recited in claim 1 which comprises the steps of dissolving sodium hydroxide in water, carrying out the reaction step by adding the aqueous solution of sodium hydroxide dropwise to said reaction zone, and in which the contents of said reaction zone are stirred during the reaction step.
• a solution as recited in claim 26 and including a wetting agent 9. A solution as recited in claim 26 and including a wetting agent.
• a solution as recited in claim 13 and including a wetting agent 14.
• a solution as recited in claim 17 and including a wetting agent are provided.
• a source of plating current and means providing current flow communication from said source to said anode the steps which comprise making said article the cathode in an aqueous solution as recited in claim 1?, directing a plating current from said source to said anode through flow communication means, and plating tin from said anode onto said article.
• a method as recited in claim 21 which includes the additional step of sequentially applying and interrupting plating current through said flow communication means.
• a method as recited in claim 23 in which said sequence provides for the application of current for a period of time between about 10 and 20 seconds, and the interruption of current for a period of time of between about 1 and 5 seconds.
• a method as recited in claim 25 which includes the additional step of dissolving sodium hydroxide in water, and in which said reacting step is carried out by adding the aqueous solution of sodium hydroxide dropwise to said reaction zone, and in which the contents of said reaction zone are stirred during the said reacting step.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
• Furan Compounds (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Cited By (25)

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Citations (3)

• 1970
  • 1970-05-06 US US35261A patent/US3634212A/en not_active Expired - Lifetime
• 1971
  • 1971-04-14 ZA ZA712389A patent/ZA712389B/xx unknown
  • 1971-04-23 JP JP2662471A patent/JPS5524512B1/ja active Pending
  • 1971-04-28 ES ES390675A patent/ES390675A1/es not_active Expired
  • 1971-04-30 BR BR2639/71A patent/BR7102639D0/pt unknown
  • 1971-05-04 SE SE7105758A patent/SE375340B/xx unknown
  • 1971-05-05 CA CA112,203A patent/CA988452A/en not_active Expired
  • 1971-05-05 NL NL7106161A patent/NL7106161A/xx active Search and Examination
  • 1971-05-05 GB GB1338471*[A patent/GB1311424A/en not_active Expired
  • 1971-05-05 DE DE2122263A patent/DE2122263C2/de not_active Expired
  • 1971-05-06 FR FR7116345A patent/FR2088388B1/fr not_active Expired

Patent Citations (3)

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