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
  • C23C18/42—Coating with noble metals
  • C23C18/44—Coating with noble metals using reducing agents

Definitions

• Electroless methods of palladium deposition known heretofore have not been successful in producing relatively thick, continuous coatings of palladium directly on copper and copper-rich alloys.
• copper acts as a poison to halt the catalytic and autocatalytic deposition of the palladium.
• Another object of the invention is to provide a novel autocatalytic process for the electroless deposition of palladium on copper-rich metallic substrates.
• the invention also contemplates providing a novel process for producing metallic electronic components having a copper-rich base and a surface of palladium metal.
• the present invention contemplates a process for the electroless deposition of palladium which comprises establishing an aqueous bath containing about 100 to about 350 grams per liter (g.p.l.) of ammonia substantially as ammonium hydroxide, up to about 80 g.p.l. of ethylenediaminetetraacetic acid (E.D.T.A.), about 0.04 to about 0.50 g.p.l. of unsymmetrical dimethylhydrazine (U.D.M.H.) and about 1 to about 20 g.p.l.
• E.D.T.A. ethylenediaminetetraacetic acid
• U.D.M.H. unsymmetrical dimethylhydrazine
• divalent palladium added advantageously as tetramminepalladium (II) chloride, immersing or dipping a body having a catalytic surface in said aqueous bath while maintaining the temperature of said bath at about 68 C. to about 100 C. to effect catalytic and autocatalytic deposition of metallic palladium from said bath on said surface while maintaining the concentration of U.D.M.H. within the aforesaid range.
• the present invention also contemplates the palladium bath which contains water, ammonia, divalent palladium and U.D.M.H. as essential ingredients.
• Objects to be plated in the bath of the present invention and according to the process of the present. invention must have a surface of a catalytic metal such as aluminum, chromium, cobalt, copper, gold, iron, molybdenum, nickel, palladium, platinum, ruthenium, silver, tin, tungsten, and alloys rich in cobalt, nickel and/or copper.
• a catalytic metal such as aluminum, chromium, cobalt, copper, gold, iron, molybdenum, nickel, palladium, platinum, ruthenium, silver, tin, tungsten, and alloys rich in cobalt, nickel and/or copper.
• a catalytic metal such as aluminum, chromium, cobalt, copper, gold, iron, molybdenum, nickel, palladium, platinum, ruthenium, silver, tin, tungsten, and alloys rich in cobalt, nickel and/or copper.
• Such objects can be composed of such a cata
• Objects made of materials such as glass, plastics and ceramics which do not catalyze the reduction of palladium can be coated with a preliminary deposit of a catalytic substance such as nickel, silver, palladium, etc., and thus, by this means, it is possible in accordance with the present invention to chemically deposit smooth and adherent plates of palladium on substantially any object.
• a catalytic substance such as nickel, silver, palladium, etc.
• a bath for the chemical deposition of palladium in accordance with the present invention is advantageously made by dissolving tetramminepalladium II) chloride in an aqueous solution of ammonium hydroxide to which is added E.D.T.A. as the disodium salt.
• Palladous palladium can also be added to the ammoniacal bath of the present invention (that is, an alkaline bath containing ammonium hydroxide or free ammonia) as palladous chloride and palladous nitrate.
• the bath can be employed statically or in a dynamic system such as in a rotating barrel.
• the deposition bath When objects are ready to be plated, that is, when they have been carefully cleaned in the manner normal to electroplating techniques, the deposition bath is brought to or maintained at operating temperature and the requisite amount of U.D.M.H. is added to the bath. The object or objects to be plated are then brought in contact with said bath. As plating progresses, periodic additions of U.D.M.H. should be made to the bath so that the concentration thereof is maintained within the required limits. In general, plating resulting from chemical deposition in the bath proceeds at a deposition rate of about 40 to about 60 microinches per hour. At these plating rates it has been found to be advantageous to add about 0.48 gram of U.D.M.H.
• the proportions of ingredients in the aqueous baths of the present invention are important in that if divalent palladium and U.D.M.H. are present in too large a concentration, the baths will tend to decompose spontaneously. On the other hand, if too little of these ingredients are present, the plating rate will be very slOW. Too little amine, e.g., ammonia, also causes low plating rates. Amounts of ammonia in excess of about 280 g.p.l. are usually not advantageous in that at the operating temperabetter understanding of the'invention, the following illustrative examples are given:
• Example I An aqueous solution containing g.p.l. of palladous palladium, 280 g.p.l. of ammonium hydroxide and 8 g.p.l. of the disodium salt of E.D.T.A. was placed in a rotatable plating barrel and maintained at a temperature of 75 C. Enough U.D.M.H. was added to provide a concentration of about 0.086 g.p.l. thereof in the solution. A brass object having a surface area of 500 cm. was thoroughly cleaned and placed in the solution in the barrel. The barrel was then rotated and at fifteen minute intervals, about 0.06 gram of U.D.M.H. was added to the solution. After one hour, the brass sample exhibited an adherent metallic deposit of palladium about 43 microinches thick.
• Example II A bronze object having a surface area of about 500 cm. was suspended in :a. U.D.M.H. containing solution as em ployed in Example I. The solution was maintained at 85 C. and the concentration of U.D.M.H. was maintained. Over a period of time, an adherent deposit of palladium metal was obtained on the bronze sample.
• Example 111 After being suspended for one hour at 90 C. in an aqueous solution containing the same amounts of U.D.M.H., ammonium hydroxide and the disodium salt of E.D.T.A. as employed in Example I but containing 10 g.p.l. of palladous palladium, a brass object having a surface area of 500 cm. was found to have an adherent deposit of metallic palladium about 59 microinches thick.
• Example IV To an aqueous solution containing 5 g.p.l. of palladous palladium, about 280 g.p.l. of ammonium hydroxide and about 0.08 g.p.l. of U.D.M.H. in a rotatable barrel, was introduced a brass object having a surface area of about 500 cm. The barrel was rotated for about one hour while the temperature of the solution was maintained at about 83 C. and while the concentration of U.D.M.H. was maintained by additions every fifteen minutes of about 0.06 gram of U.D.M.H. After one hour, the object was found to have an adherent plate of metallic palladium about 45 microinches thick.
• Example V Boiling aqueous solutions containing 10 g.p.l. of palladous palladium, 280 g.p.l. of ammonium hydroxide and 0.08 g.p.l. of U.D.M.H. were employed to plate copper and bronze objects.
• the objects each had about 500 cm. surface area.
• the copper object suspended in the bath exhibited a metallic palladium deposit about 60 microinches thick
• the bronze object, plated in a rotating barrel exhibited a metallic palladium deposit about 52 microinches thick.
• the present invention is particularly applicable to the production of electrical and/or electronic components made of copper and coated with an adherent bright deposit of palladium.
• other ingredients can be employed in the bath.
• mole for mole amounts of stabilizing substances such as ammonium chloride and ammonium sulfate can be employed in place of or in addition to E.D.T.A.
• Other amines such as aminoethyl ethanolamine and/ or amylamine can be employed mole for mole in addition to or in place of part of the ammonium hydroxide.
• substances for brightening, leveling, etc. can be employed in the bath.
• the present invention is not to be confused with processes for electroless deposition of palladium involving the use of hydrazine.
• Objects made of copper or alloys rich in copper cannot be directly coated with palladium from ammoniacal baths containing high concentrations of ammonia and containing hydrazine as the sole agent for reducing palladium ion to palladium metal.
• the process of the present invention is particularly adapted to be employed in the plating of electrical and electronic components made of copper and/or copper-rich alloys.
• a bath for the electroless deposition of palladium comprising an aqueous solution containing about 1 to about 20 grams per liter of divalent palladium, about 0.04 to about 0.50 gram per liter of unsymmetrical dimethylhydrazine, an amine selected from the group consisting of ammonia, aminoethyl ethanolamine and amylamine in an amount equivalent in molar concentration to about 100 to about 350 grams per liter of ammonia and a stabilizing agent selected from the group consisting of ammonium chloride, ammonium sulfate and ethylenediaminetetraacetic acid in an amount equivalent in molar concentration to up to about grams per liter of ethylenediaminetetraacetic acid.
• a bath for the electroless deposition of palladium comprising an aqueous solution containing about 1 to 20 grams per liter of divalent palladium, about 0.04 to about 0.50 gram per liter of unsymmetrical dimethylhydrazine, about to about 350 grams per liter of ammonia and up to about 80 grams per liter of ethylenediaminetetraacetic acid.
• a bath for the electroless deposition of palladium comprising anaqueous solution containing about 5 to about 10 grams per liter of divalent palladium, about 0.05 to about 0.45 gram per liter of unsymmetrical dimethylhydrazine, about to about grams per liter of ammonia and about 5 to about 24 grams per liter of ethylenediaminetetraacetic acid.
• a process for the electroless deposition of palladium which comprises establishing an aqueous bath containing about 1 to about 20 grams per liter of divalent palladium, about 0.04 to about 0.50 gram per liter of unsymmetrical dimethylhydrazine, an amine selected from the group consisting of ammonia, aminoethyl ethanolamine and amylamine in an amount equivalent in molar concentration to about 100 to about 350 grams per liter of ammonia and a stabilizing agent selected from the group consisting of ammonium chloride, ammonium sulfate and ethylenediaminetetraacetic acid in an amount equivalent in molar concentration to up to about 80 grams per liter of ethylenediaminetetraacetic acid and placing a body having a catalytic surface in contact with said aqueous bath while maintaining the temperature of said bath at about 68 C. to about 100 C. to effect a deposition of metallic palladium from said bath on said surface and while replenishing said bath with unsymmetrical dimethylhydn
• a process for the electroless deposition of palladium which comprises establishing an aqueous bath containing about 100 to about 350 grams per liter of ammonia, up to amout 80 grams per liter of ethylenediaminete-traacetic acid, about 0.04 to about 0.50 gram per liter of unsymmetrical dimethylhydrazine and about 1 to about 20 grams per liter of divalent palladium, placing a body having a catalytic surface in contact with said aqueous bath while maintaining the temperature of said bath at about 68 C. to about 100 C. to effect a deposition of metallic palladium from said bath on said surface and while replenishing said bath with unsymmetrical dimethylhydrazine to maintain the concentration thereof within said range of about 0.04 to about 0.50 gram per liter.
• a process for the electroless deposition of palladium which comprises establishing an aqueous bath containing about 120 to about 170 grams per liter of ammonia, about 5 to about 24 grams per liter of ethylenediaminetetraacetic acid, about 0.05 to about 0.45 gram per liter of unsymmetrical dimethylhydrazine and about 5 to about 10 grams per liter of divalent palladium, placing a body having a catalytic surface in contact with said aqueous bath While maintaining the temperature of said bath at about 68 C. to about 100 C. to effect a deposition of metallic palladium from said bath on said surface and while replenishing said bath with unsymmetrical dimethylhydrazine to maintain the concentration thereof within said range of about 0.05 to about 0.45 gram per liter.

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• Chemical & Material Sciences (AREA)
• 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)
• Electroplating And Plating Baths Therefor (AREA)

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Cited By (10)

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• 1963
  • 1963-03-26 US US267947A patent/US3274022A/en not_active Expired - Lifetime
• 1964
  • 1964-03-10 GB GB10064/64A patent/GB994560A/en not_active Expired
  • 1964-03-19 DE DEJ25485A patent/DE1247804B/de active Pending
  • 1964-03-23 NL NL6403078A patent/NL6403078A/xx unknown
  • 1964-03-26 BE BE645775A patent/BE645775A/xx unknown

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