Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
  • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
  • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
  • C23C18/36—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents using hypophosphites
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/38—Coating with copper
  • C23C18/40—Coating with copper using reducing agents
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/38—Coating with copper
  • C23C18/40—Coating with copper using reducing agents
  • C23C18/405—Formaldehyde
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/48—Coating with alloys
  • C23C18/50—Coating with alloys with alloys based on iron, cobalt or nickel
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/52—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating using reducing agents for coating with metallic material not provided for in a single one of groups C23C18/32 - C23C18/50

Definitions

• the stability of an electroless plating solution can be substantially increased by the addition of a covalent mercury compound alone as a primary stabilizer, or preferably, by the addition of the mercury compound as a secondary stabilizer in combination with a prior art stabilizer as primary stabilizer.
• the combination of stabilizers provides a synergism with stability substantially improved over that obtainable with either component of the combination alone.
• This invention relates to a metal-depositing composition and more particularly, to an electroless metal plating solution having extended life and temperature tolerance and characterized by the addition of a stabilizer comprising a covalent mercury compound alone or in combination with a prior art stabilizer.
• Electroless metal deposition refers to the chemical plating of a metal over an active surface by chemical reduction in the absence of an external electric current. Processes and compositions useful therefor are known, are in substantial commercial use, and are described in numerous publications. For example. compositions for depositing electroless copper are described in U.S. Pat. Nos. 2,938,805; 3,011,920; and 3,383,224 and compositions for depositing electroless nickel are described in U.S. Pat. Nos. 2,690,401; 2,690,402;
• Known electroless metal deposition solutions generally comprise at least four ingredients dissolved in a solvent, usually water. They are (1) a source of the metal ions, (2) a reducing agent such as formaldehyde for copper or hypophosphite for nickel, (3) an acid or hydroxide pH adjuster to provide required pH, and (4) a complexing agent for metal ions sufficient to prevent their precipitation in solution.
• a solvent usually water.
• a source of the metal ions usually water.
• a reducing agent such as formaldehyde for copper or hypophosphite for nickel
• an acid or hydroxide pH adjuster to provide required pH
• (4) a complexing agent for metal ions sufficient to prevent their precipitation in solution.
• suitable complexing ions for electroless metal solutions are described in the above noted publications and also in U.S. Pat. Nos. 2,874,072; 3,075,856; and 8,075,855 also incorporated herein by reference.
• the complexing agent is helpful but not a necessity.
• electroless metal solutions have been used for many years, the commercially used formulations have not been fully satisfactory for several reasons. Among these are relatively slow deposition rates and bath instability. It has been shown that plating rate is dependent to some extent, upon the concentration of the reducing agent in the plating solution and that increased concentration will generally result in an increased rate of deposition. However, increased concentration of reducing agent also results in decreased bath stability. This is evidenced by a decrease in the time in which the plating solution will undergo uncontrollable decomposition (trigger).
• stabilizing agents useful for stabilizing a solution of one metal may or may not be useful for the stabilization of a solution of a different metal.
• thio compounds such as thiourea and alkali thiosulfates are useful stabilizers for both nickel and copper solutions while cyanide compounds are used only for the stabilization of copper solutions.
• the present invention provides an electroless metal solution comprising: l) a source of metal ions, (2) a reducing agent therefor such as formaldehyde for copper or hypophosphite for nickel, (3) a pH adjuster, (4) a complexing agent for the metal ions sufficient to prevent their precipitation in solution where necessary, and (5) a stabilizer for the solution which may be a covalent mercury compound alone, as a primary stabilizer or in combination with a prior art stabilizer.
• covalent mercury compound is believed to be responsible for increased bath stability.
• a covalent mercury compound is defined as one that does not dissociate in an electroless plating solution to yield mercury ions (Hg**).
• the mercury compound contemplated may be represented by the formula R- HgR where R represents a radical such as alkyl including cyloalkyl, aryl, alkaryl, aralkyl, alkoxy, aryloxy, heterocyclic and the like, and R represents the same radicals as R and in addition polar groups such as NO SO OH, and metal salts such as sodium salts, COOH and metal salts such as sodium salts, NH halides such as Cl, Br and l, CN, and the like.
• R represents a radical such as alkyl including cyloalkyl, aryl, alkaryl, aralkyl, alkoxy, aryloxy, heterocyclic and the like
• R represents the same radicals as R and in addition polar groups such as NO SO OH, and metal salts such as sodium salts, COOH and metal salts such as sodium salts, NH halides such as Cl, Br and l, CN, and the like.
• Examples of compounds corresponding to the above formula include ethylmercuric hydroxide, ethylmercuric iodide, mercury ethylmercaptide (ic), mercury phenylmercaptide (ic), methylmercuric chloride, methylmercuric iodide, diisopropylmercury, dimethylanilinemercury (p), dimethylmercury, dinaphthylmercury (a), dinaphthylmercury (B), dipropylmercury, ditolylmercury (o), ditolylmercury (m), ditolylmercury (p), phenylmercuric bromide, phenylmercuric chloride, phenylmercuric cyanide, phenylmercuric iodide, phenylmercuric nitrate, tolylmercuric bromide (p), biphenylmercury, chloromercuriphenol (o
• the covalent mercury compound contains polar groups either attached to the radical R or as represented by R. These polar groups enhance the solubility of the covalent mercury compounds in solution.
• Preferred polar groups are OH and alkali metal salts of COOH and SO OH.
• mercury compounds are only poorly soluble in aqueous solutions and many are considered insoluble.
• the mercury compound for purposes of the present invention, is required in amounts of only parts per million. Consequently, mercury compounds considered insoluble in aqueous solution may be soluble to the extent that they yield mercury ions in concentrations sufficient for purposes of the present invention. Mercury compounds soluble in aqueous solution are preferred.
• covalent mercury compounds are not believed to be catalytic poisons, their concentration in solution is not critical. Frequently, trace quantities are suitable. A preferred range comprises from about l to parts per million. However, amounts up to saturation in solution may be used or amounts in excess of saturation may be used, the excess serving as a source of the mercury compound for replenishment.
• the covalent mercury compound is used as a stabilizer in combination with a prior art stabilizer.
• Materials known to the art as catalytic poisons to the deposition of electroless metal are frequently used in controlled amounts as stabilizers for electroless plating solutions.
• Perhaps the most widely used group of compounds of this nature are the divalent sulphur-containing compounds, many ofwhich are disclosed in U.S. Pat. No. 3,361,540, incorporated herein by reference.
• sulphur compounds are the inorganic sulfides such as sodium sulfide, potassium sulfide, sodium polysulfide, and potassium polysulfide; organic and inorganic thio compounds such as sodium thiocyanate, potassium thiocyanate, potassium dithionate, sodium thiosulfate, and potassium thiosulfate; and organic sulphur containing compounds such as thiourea, 2- mercaptobenzothiazole, l,2-ethanedithiol, 1,2- benziosothiazane, methionine, 2,2'thiodiethanol, dithioglycol, and thioglycollic acid.
• inorganic sulfides such as sodium sulfide, potassium sulfide, sodium polysulfide, and potassium polysulfide
• organic and inorganic thio compounds such as sodium thiocyanate, potassium thiocyanate, potassium dithionate, sodium
• the amount of the sulfur compound used in combination with the mercury compound is small and will vary depending upon the particular compound used. Typically, the sulfur compound is present in an amount less than that which will not stop deposition of the plating metal. Generally, the amount may vary from a trace to about 300 parts per million dependent upon the sulfur compound used.
• One other class of stabilizers comprises the water-soluble cyanide compounds defined broadly to include nitriles and dinitriles set forth in U.S. Pat. No. 3,3l0,430. Typical of such compounds are alkali metal cyanides such as sodium and potassium cyanide; nitriles such as alpha-hydroxynitrile, e.g., glyconitrile and lactonitrile, and dinitriles such as im inodiacetonitrile and 3 ,3 iminodipropionitrile. The cyanide compound is used in an amount about equal to that of the divalent sulfur compound.
• R-C 5 CH or RC E CR where each R is individually selected from the class of lower monovalent hydroxyalkyl, cyclohydroxyalkyl or hydroxyalkyl ether.
• R is individually selected from the class of lower monovalent hydroxyalkyl, cyclohydroxyalkyl or hydroxyalkyl ether. Examples include ethynyl cyclohexanol, methyl butynol, methyl pentynol, dimethyl hexynol, 2-butyne-l,4-diol, dimethyl hexynediol, propargyl alcohol, hexynol and ethyl octynol.
• each of R,R and R" can be aryl or aliphatic including cycloaliphatic substituted with a watersolubilizing group such as hydroxyl and carboxyl.
• acetylinic compounds contemplated will be referred to by the term solution soluble acetylinic compounds.
• iodate compounds such as sodium and potassium iodate and Pb ions are useful stabilizers for electroless nickel solutions. Both iodate and Pb ions are used in amounts of a few parts per million, preferably less than 50 parts per million. Additional examples of metals useful as stabilizers for electroless copper solutions are disclosed in the aforementioned U.S. Pat. No. 3,310,430.
• An electroless plating solution stabilized with a covalent mercury compound in accordance with this invention is used to deposit metal in the same manner as any prior art electroless solution.
• the surface of the part to be plated should be free of grease and contaminating material. Where a nonmetallic surface is to be plated, the surface area to receive the deposit must first be sensitized to render it catalytic to the reception of the electroless metal as by the well-known treatment with an acidic aqueous solution of stannous chloride followed by treatment with dilute aqueous acidic solution of palladium chloride.
• catalyzed cloth was prepared by treating a cotton fabric according to the following sequence of steps:
• rate was determined by plating over a phenolic substrate using the following procedure:
• Catalyzed cloth was plated with the above formulation with stabilizing additives added in amounts and with results as set forth in the following table:
• a sodiunvpotus ium turtrute double salt A sodiunvpotus ium turtrute double salt.
• Catalyzed cloth is plated by immersion in the above solution containing stabilizers in amounts and with results as set forth in the following table:
• Catalyzed cloth was plated by immersion in the above formulation with stabilizers added in amounts and with results as set forth in the following table:
• Bath No. 8 illustrates the substantial improvement and the synergism resulting from the combination of the covalent mercury compound with a prior art stabilizing compound.
• Catalyzed cloth was plated by immersion in the above formulation containing stabilizers in amounts and with results as set forth in the following table;
• Catalyzed cloth was plated by immersion in the above solution containing stabilizers in amounts and with results as set forth in the following table:
• Catalyzed cloth was immersed in the above formulation with the result that hath decomposition occurred in 5 to 6 minutes. With the addition of 60 ppm. phenylmercuric acetate to the formulation, catalyzed cloth was left in the solu tion for a period in excess of 1 hour without bath decomposition.
• Covalent mercury compounds used alone are primary stabilizers for electroless metal solutions.
• Covalent mercury compounds in combination with prior art stabilizers for electroless metal solutions exhibit a synergism that improves stability of solution to an extent greater than that obtainable with either the mercury compound or the prior art stabilizer used alone.
• a solution soluble covalent mercury compound corresponding to the formula RHgR where R is a covalently bonded organic radical selected from the group of alkyl, cycloalkyl, aryl, alkaryl, aralkyl, alkoxy, aryloxy and heterocyclic radicals and R is the same as R or a polar group selected from the group of NO SO. ,OH and alkali metal salts thereof, COOH and alkali metal salts thereof, NH CN and halide in a small but effective amount capable of providing increased bath stability.
• composition of claim 1 where R is a polar group 2. The composition of claim 1 where R is a polar group.
• composition of claim 1 where the covalent mercury compound is in solution in an amount varying from 1 to 100 parts per million.
• composition of claim 1 further characterized by the addition of a second stabilizer for an electroless copper solution.
• composition of claim 2 where the second stabilizer is selected from the group consisting of divalent sulfur compounds, cyanide compounds including nitriles and dinitriles and acetylinic compounds.
• composition of claim 2 where the acetylinic compound corresponds to one of the following formulas:
• R, R and R" are radicals selected from the group of monovalent hydroxyalkyl, cyclohydroxyalkyl and hydroxyalkyl ether.
• an aqueous electroless copper solution comprising a source of cupric ions, a reducing agent therefor, a complexing agent for the cupric ions in an amount sufficient to prevent precipitation of the cupric ions in solution and a source of hydroxide ions; the improvement comprising the addition of phenyl mercuric acetate in a small but effective amount capable of providing increased bath stability.
• an aqueous electroless nickel solution comprising a source of nickel ions, a hypophosphite reducing agent therefor, and a pH adjuster; the improvement comprising a solution soluble covalent mercury compound corresponding to the formula RHg-R' where R is a covalently bonded organic radical selected from the group of alkyl, cycloalkyl, aryl, alkaryl, aralkyl, alkoxy, aryloxy and heterocyclic radicals and R is the same as R or a polar group selected from the group of NO SO OH and alkali metal salts thereof, COOH and alkali metal salts thereof, -NH CN and halide in a small but effective amount capable of providing increased bath stability.
• RHg-R' where R is a covalently bonded organic radical selected from the group of alkyl, cycloalkyl, aryl, alkaryl, aralkyl, alkoxy, aryloxy and heterocyclic radicals and R is the same
• composition of claim 9 where the covalent mercury compound is in solution in an amount varying from 1 to parts per million parts of solution.
• composition of claim 9 including a complexing agent for nickel ions in an amount capable of preventing precipitation of the nickel ions in solution.
• composition of claim 7 in combination with a second stabilizer for electroless nickel solutions.
• composition of claim 2 where the second stabilizer is selected from the group consisting of divalent sulfur compounds, lead ions, iodate compounds and acetylinic compounds.
• composition of claim 3 where the acetylinic compound corresponds to one ofthe following generic formulas:
• composition of claim 7 where the second stabilizer is lead ions.
• composition of claim 7 where the second stabilizer is a thio compound is a thio compound.
• composition of claim 7 where the second stabilizer is an iodate compound.
• an aqueous electroless nickel solution comprising a source of nickel ions, a hypophosphite reducing agent therefor, and a pH adjuster; the improvement comprising phenylmercuric acetate in solution in a small but effective amount capable of providing increased bath stability.

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• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemically Coating (AREA)

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Cited By (9)

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• 1970
  • 1970-05-21 US US39503A patent/US3649308A/en not_active Expired - Lifetime
  • 1970-05-25 NL NL7007510A patent/NL7007510A/xx unknown
  • 1970-05-27 FR FR7019372A patent/FR2088202B1/fr not_active Expired
• 1971
  • 1971-04-15 NL NL717105020A patent/NL144667B/xx unknown
  • 1971-05-14 FR FR7117546A patent/FR2091636A5/fr not_active Expired
  • 1971-05-17 DE DE2124331A patent/DE2124331C3/de not_active Expired
  • 1971-05-17 DE DE19712124330 patent/DE2124330B2/de not_active Withdrawn
  • 1971-05-18 SE SE06452/71A patent/SE366069B/xx unknown
  • 1971-05-21 GB GB1643771A patent/GB1324895A/en not_active Expired
  • 1971-05-21 GB GB1643571A patent/GB1324827A/en not_active Expired

Patent Citations (1)

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