US 2002.0002128A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2002/0002128A1 Gernon et al. (43) Pub. Date: Jan. 3, 2002 (54) AQUEOUS SOLUTIONS CONTAINING Related U.S. Application Data DITHIONIC ACID AND/OR METAL DTHONATE (63) Non-provisional of provisional application No. 60/186,097, filed on Mar. 1, 2000. (76) Inventors: Michael D. Gernon, Upper Providence, Publication Classification PA (US); Sandra L. Bodar, 7 Coulommiers (FR) (51) Int. Cl." ....................................................... C11D 1100 (52) U.S. Cl. .............................................................. 510,363 Correspondence Address: Gilbert W. Rudman (57) ABSTRACT ATOFINA Chemicals, Inc., Patent Department This invention relates to Solutions of dithionic acid and/or 26th Floor dithionate Salts for use in metal finishing processes Such as 2000 Market Street those used for the cleaning, activating, electroplating, elec Philadelphia, PA 19103-3222 (US) troless plating, conversion coating and/or other pre-treat ment or post-treatment of a metallic Surface. In particular the (21) Appl. No.: 09/791,224 Solutions are a useful electrolyte for the electroplating of metallic coatings, especially, Sn, Cu, Ni, Zn and precious (22) Filed: Feb. 22, 2001 metals, onto metal or plastic Substrates and/or other Surfaces. US 2002/0002128A1 Jan. 3, 2002 AQUEOUS SOLUTIONS CONTAINING DITHIONIC 0014) Another embodiment is a surface cleaning solution ACID AND/OR METAL DITHIONATE composition for a Substrate, other than copper, which con tains metal or ammonium dithionate Salts. REFERENCE TO RELATED APPLICATION 0015. Another embodiment is an aqueous solution of 0001. This application claims the benefit of United States ammonium, IA metal and/or IIA metal dithionate Salts for Provisional Application Ser. No. 60/186,097, filed Mar. 1, cleaning and activating metal, plastic and/or other Surfaces. 2OOO. 0016. Another embodiment is an electroless or immer BACKGROUND OF THE INVENTION Sion plating composition which contains free dithionic acid. 0002) 1. Field of the Invention 0017 Another embodiment is an electroless or immer Sion plating composition, other than one for nickel or 0003. This invention relates to solutions useful in metal palladium, which contains dissolved metal or ammonium finishing processes. In particular it relates to Solutions con dithionate Salts. taining dithionic acid and/or dithionate Salts. 0018. Another embodiment is an electroless or immer 0004 2. Description of the Prior Art Sion plating composition for nickel or palladium, which 0005 Known plating electrolytes include, for instance, contains dissolved nickel dithionate, palladium dithionate, alkaline cyanide, acidic Sulfate, acidic phosphate, acidic other metal dithionate or ammonium dithionate Salts at fluoborate and acidic methaneSulfonate Systems. These vari concentrations greater than 0.1 M. ous electrolytes are Selected by industrial practitioners of 0019. Another embodiment is the use of a solution con metal finishing based on the relative advantages they offer taining dissolved metal or ammonium dithionate as a rust for performance, quality and environmental compatibility. removing agent. 0006 The industry is constantly seeking new and improved electrolyte Systems for the finishing of metal 0020. Another embodiment is the use of compositions of substrates which allow for favorable differentiation of plat the invention as an electroless or immersion plating Solution ing processes relating, for instance, to electroplating Speed, in an electroless or immersion tin plating System. performance and electrodeposit quality. 0021 Another embodiment is an electroplating process 0007 Kubo, M.; Kamitamari, T.; Hotsuta, T., Masamoto, employing a composition of the invention. H.; Jpn. Kokai Tokkyo Koho JP 08269727 A2, Oct. 15, 0022. Another embodiment is a metal, semiconductor or 1996, assigned to Uemura Kogyo, discloses the use of an plastic Surface treatment process employing a composition inorganic Sulfur compound Selected from thiosulfate, poly of the invention. thionate, dithionite, Sulfite and dithionate at an amount of 0.01 to 10 mmol/L as an additive in an electroless palladium 0023. Another embodiment is a metal finishing process coating bath containing a palladium Salt, a reductant Selected employing a composition of the invention. from HPO and its salts, HPO and its salts, hydroborides, and amine borane, and complexing agent Selected from NH DETAILED DESCRIPTION OF THE and amines. INVENTION 0008 Uchida, Hetal, Kokai, Tokkyo Koho JP 08269726 0024. The description which follows sets forth additional A2 and Uchida, H et al, German Offen. DE 19639174 A1 features and advantages of the invention which, in part, will both disclose a Solution for electroleSS coating of nickel. The become apparent from the description or learned by practice Solution contains a water Soluble nickel Salt, a reducing of the invention. The skilled artisan will realize the objec agent, a complexing agent and a compound having S-S tives and other advantages of the invention obtained by bonds, Such as, thiosulfate, dithionate, dithionite, and poly process and compositions of matter particularly pointed out thionate. in the written description and claims hereof. SUMMARY OF THE INVENTION 0025 Dithionic acid has the molecular formula HSO (CAS Registry # 14970-71-9). Dithionic acid and salts 0009. One embodiment of the invention is an aqueous derived from dithionic acid are the basis of the compositions Solution of dithionic acid and/or dithionate salts which and processes of the present invention. Serves as a useful electrolyte for the electroplating of metal lic coatings, especially, Sn, Cu, Ni, Zn and precious metals, 0026 Alkaline, neutral and acidic dithionate based elec onto metal or plastic Substrates and/or other Surfaces. trolytes offer numerous advantages with respect to power consumption, process performance and quality for a number 0.010 Another embodiment is a metal finishing solution of industrially important metal finishing processes. composition which contains free dithionic acid. 0027 “Electrolyte” as used herein means any conducting 0.011) Another embodiment is an electroplating solution aqueous or mixed aqueous Solution which can be used as the composition which contains free dithionic acid. basis for a formulated metal finishing product. 0012 Another embodiment is an electroplating solution 0028 “Metal finishing” as used herein is meant to composition which contains metal or ammonium dithionate encompass all processes used for the cleaning, activating, Salts. electroplating, electroleSS plating, conversion coating and/or 0013 Another embodiment is a surface cleaning solution other pre-treatment or post-treatment of a metallic Surface, composition which contains free dithionic acid. Semiconductor, glass or hard plastic. US 2002/0002128A1 Jan. 3, 2002 0029. The differentiation between an additive and an metal to be electroplated and to, in general, create a Solution electrolyte component as based on concentration is not which allows for adequate performance. definite. An additive is Something which is added to enhance certain aspects of the Surface (cleaned, electroplated or 0037. The metal salt source of the metal to be electro whatever) quality. An electrolyte component is something plated has an obvious function. which provides for solubility, conductivity, process effi 0038. Additives are used mostly to improve the quality of ciency, deposit quality and other things. the electrodeposited metal(s) through specific Surface effects. For instance, Surface tension lowering additives are 0030 The following ranges are indicated: used to, among other things, allow for the more efficient 0.031) For Electroplating, Electroless Plating, Immersion ejection of gas bubbles from the Surface being electroplated. Plating, one can use dithionic acid up to 60% by weight, Such gas bubbles, if they are not properly handled, can cause preferred is 0.1% to 25% by weight, more preferred is 1% pits in the electroplated coating. to 18% by weight. Aqueous dithionic acid Solutions become 0039. In this invention, dithionic acid and/or metal leSS Stable as the acidity of the Solution is increased. The dithionates, Such as the Sodium, potassium, calcium, copper, preferred range for dithionic acid is up to 25% by weight Zinc, nickel, tin, lead, ammonium and/or other metal dithion (stable in this range), but higher levels are occasionally ates, are added to electroplating formulations as a means of useful. The instability of the acid at higher free acid levels improving the performance of these formulations. is Something that needs to be balanced against its perfor mance at higher acid levels. Metal dithionates can be used 0040 Cleaning and activation solutions do not require a up to their saturation solubility, preferred is 0.01 M to 2 M Source of metal ions for deposition, but Such Systems do in metal, more preferred is 0.1M to 1 M in metal. The metals require an optimized electrolyte composition. In this inven employed may be the metals plated and/or they may be other tion, dithionic acid and/or metal dithionates, Such as the metals used to provide peripheral benefits like conductivity. Sodium, potassium, calcium, copper, Zinc, nickel, tin, ammo A generally preferred range for the metal dithionates added nium and/or other metal dithionates, are added to the clean for peripheral benefits is from 0.001 M to 5 M in metal, ing and/or activating Solutions as a means of improving the preferred is 0.01 M to