US3441428A - Low temperature electroless plating - Google Patents

Low temperature electroless plating Download PDF

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Publication number
US3441428A
US3441428A US486602A US3441428DA US3441428A US 3441428 A US3441428 A US 3441428A US 486602 A US486602 A US 486602A US 3441428D A US3441428D A US 3441428DA US 3441428 A US3441428 A US 3441428A
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United States
Prior art keywords
nickel
plating
hypophosphite
solution
ammonium
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Expired - Lifetime
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US486602A
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English (en)
Inventor
George C Reinhard
Michael W O'mara
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GEORGE C REINHARD
MICHAEL W O MARA
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GEORGE C REINHARD
MICHAEL W O MARA
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    • 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
    • C23C18/1601—Process or apparatus
    • C23C18/1617—Purification and regeneration of coating baths

Definitions

  • ABSTRACT OF THE DISCLOSURE A process of plating metals on the cleaned surface of an article of non-conductive material wherein said article is immersed in a solution consisting essentially of nickel and ammonium cations and hypophosphite anions and substantially devoid of chloride and sulfate ions.
  • the solution is maintained in the temperature range of 70 F.-'l40 F., and replenished from time to time with additional amounts of hypophosphite, ammonia and nickel.
  • This invention relates to electroless plating of metals on physical surfaces and more particularly to the electroless plating of the metals such as nickel and cobalt, by means of chemical reduction of the metal ions to elemental metal, using such as hypophosphite as the reducing anion.
  • reaction is catalyzed by certain metals it is termed one of catalytic plating. And because the metals deposited are also catalytic to the reaction, it is more specifically termed autocatalytic.
  • ABS acrylonitrile-butadiene-styrene copolymer type of plastic
  • ABS acrylonitrile-butadiene-styrene copolymer type of plastic
  • ABS plastics A demand for such articles including materials such as ABS plastics already exists but is prevented from realizing full attainment, or stimulus toward full attainment, by reason of the lack of perfection of efiicient, dependable, rapid, economical plating processes.
  • the plastic, polymeric materials of an organic and semi-organic nature are generally as a class, more sensitive to the effect of heat so as to present greatly limiting conditions for their processing which make it impossible or impractical to utilize many of the solutions, processes and techniques to which metals and heat insensitive nonmetals are adaptable.
  • the degrading eflfect of heat is particularly a case in point. At temperatures far below those at which metals manifest no deleterious effect, plastics and resins do manifest effects such as softening and distortion. Not only is this manifested at elevated temperatures or under dry heat conditions but rather at temperatures, even under wet conditions, of hot to boiling water.
  • plating processing be conducted at no higher temperature than 140 F. and, of course, as close to an ambient room temperature of approximately F. as possible.
  • This rapid plating will occur at temperatures ranging from at least a minimum of ambient room temperature of about 70 F. to at least the maximum limit stated as established for plastics in general and for acrylonitrile-butadienestyrene plastic, commonly called ABS, which temperature is usually considered to be F.
  • an object of this invention is to provide improved stability of the plating solution whereby it can be used for long periods with only the necessity of replenishing reactants as they are consumed, and an object of this invention is to provide, within specified limits, an automatic pH control whereby it is not necessary to make frequent additions of alkali to maintain pH at the desired degree as is normally necessary to neutralize the acid of reaction that is characteristically formed in the hypophosphite reactions.
  • alkali salts of weak organic acids provide a buffering action for the maintenance of pH within certain limits on the acid side of the pH range. This is to prevent the rapid reduction of pH below which the plating rate is seriously reduced or prevented.
  • Other organic salts were of a type that formed complexes with the nickel, selected from a group of reactants such as hydroxyacetic, lactic, citric, and tartaric acid.
  • Pretreatment to make nonmetals and noncatalytic materials catalytic to the reaction of the applied solution at least initially and until autocatalysis sets in, is necessary.
  • Such pretreatment or preparation generally requires that the basic material be cleaned and conditioned to make the palladium more readily and more completely received by and attached to the basic material for, depending upon the thoroughness of this, rests the complete success or failure in part, of all the ensuing operations of chemical and electrodeposition of metal which follow.
  • Pretreatment is specific to each material processed.
  • organic, polymeric materials including the ABS type plastic
  • it is generally processed to remove soil, oil, grease and foreign matter using for this purpose any of the detergent alkali cleaners.
  • a mild acid rinse to neutralize the detergent alkali.
  • the material is chemically delustered or etched by wet oxidation in a bath of chromic-acid composition, usually at 140 F. maximum after which, following a thorough rinse, it is deemed satisfactorily prepared to be subjected to the treatment necessary thereafter to make it susceptible to deposition of an adherent deposit of palladium.
  • Processes utilizing proprietary and non-proprietary compositions generally consist of adsorbing to the cleaned, etched or abraded work, a film of a strong reducing agent that is capable of reducing soluble palladium salts to the elemental state.
  • a strong reducing agent that is capable of reducing soluble palladium salts to the elemental state.
  • ammonium ions stimulate reaction especially in the higher alkaline pH ranges, while certain other cations, such as barium and magnesium, influenced, for better or worse, the rate of reaction.
  • Ni/gal. at pH 8 plus A solution of nickel ammonium hypophosphite-Trace to 1 oz. (preferred) of Ni/gal. at pH 8 plus, made with ammonium hydroxide preferred in excess.
  • Example No. 1 there is introduced no extraneous anions of any kind. There is introduced as the only anion an amount of hypophosphite combined in the compound with nickel, in an amount sufficient to reduce no more than 50% of the nickel on a theoretical basis and only about one-third the amount necessary to reduce all the nickel from a practical standpoint.
  • hypophosphite This is an ideal ratio of hypophosphite to nickel with which to operate the bath initially because, being so extremely activated, or exalted, it is advisable that the concentration of hypophosphite be not augmented initially, with further additions. Since activity of these solutions in alkaline media is increased and stimulated by the absolute concentration of hypophosphite, or the ratio of hypophosphite to nickel, too high a concentration of hypophosphite contributes excessively to activity and in turn makes it so reactive as to impair stability.
  • the ratio relationship that develops is one that makes the solution more stable.
  • the hypophosphite is consumed it, of course, requires replenishment so as to effect efiicient consumption of nickel.
  • Such additions are made from time to time in the form of an alkali or ammonium salt and in an amount that will bring the ratio of hypophosphite to nickel up to the original ratio but does not exceed this original ratio and thereby contribute unduly to the instability of the solution.
  • Example No. 2 since no hypophosphite exists in the nickel compound utilized, it must be provided supplemental thereto, at the outset. Such is preferred to be initially in the same mole ratio of 1 mol. of nickel to 1 mol. of hypophosphite for the same reason of stability of solution. Also for the same reasons as detailed, the replenishment should be effected in the same general manner and of the same kind and type as stated above for Example No. 1.
  • plating occurs quickly at ambient room temperature of approximately 70. F. as is evidenced by the evolution of gas formed by reaction on the surface of the catalyzing article, and the visual change in appearance (noticeable when plating light colored plastic bodies) that is observed as the article rapidly becoming darkened and opaque on the surface, and gradually assuming a metallic lustre and appearance.
  • the high pH of the solution is automatically maintained over long periods of time.
  • the acid of reaction characteristic of these nickel-hypophosphite plating solutions, is immediately neutralized as it is formed Without effecting a reduction of the pH until the excess of ammonia has been consumed. Thereafter, the change in pH is not abrupt but is gradual as the complexed'nickel compound acts as a buffer changing gradually in pH only as combined ammonia in the complex is removed by the acid of reaction, as the nickel compound in turn is converted from highly complexed to lesser complexed compound.
  • the phosphite anion is formed as the product of reaction and increases in concentration proportionally to the amount of nickel plated.
  • this byproduct accumulating as it does, does not impair the solution or retard its performance appreciably up to a replenishment of additional nickel deposited by plating, of at least three times the original of 1 oz./ gal. nickel concentration.
  • the slight reduction in plating rate that results is readily compensated for by increase in temperature, for which ample factor is provided, or by increasing the absolute concentration of hypophosphite.
  • ammonium double salt complexes it is usual to prepare them from the normal salt, made by reacting stoichiometric proportions of nickel and anion, either by ion exchange or by reacting the acid with a suitable basic compound of nickel such as the hydroxide, carbonate, etc., by adding to the said normal salt an amount of ammonium hydroxide to form the complex of the degree and type desired.
  • the double ammonium nickel complex of the kind and type desired can be directly prepared by adding to an ammoniacal solution of the normal ammonium salt, an amount of a nickel base such as nickel carbonate, equivalent to the amount of normal ammonium salt.
  • a nickel base such as nickel carbonate
  • reaction takes place quite rapidly and proceeds to completion. The reaction is facilitated by even moderate heat and, when nickel carbonate is the base compound, rapid discharge of carbon dioxide accompanies the reaction.
  • the normal ammonium salts utilized are the hypophosphite and hydroxyacetate, respectively.
  • Hydroxyacetate has been selected as typical and is preferred for the reason that it is currently economically advantageous especially in the 70% commercial technical form that has been found suitable. It is not in any case utilized here for the reason it is normally utilized (the reason based on its known character of forming complexes of nickel in the pH range below pH 8). We do not operate in this range because the plating rate at the low temperature is inadequate and too slow.
  • replenishment nickel selected from the group consisting of nickel ammonium salt of an organic acid, nickel ammonium hypophosphite, nickel hydroxide, and nickel carbonate.
  • hypophosphite ions are provided by ammonium hypophosphite.

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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)
  • Surface Treatment Of Glass (AREA)
US486602A 1965-09-13 1965-09-13 Low temperature electroless plating Expired - Lifetime US3441428A (en)

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US48660265A 1965-09-13 1965-09-13

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US3441428A true US3441428A (en) 1969-04-29

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US (1) US3441428A (enExample)
JP (1) JPS4945209B1 (enExample)
DE (1) DE1621326A1 (enExample)
GB (1) GB1111258A (enExample)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3962495A (en) * 1972-11-08 1976-06-08 Rca Corporation Method of making duplicates of optical or sound recordings
US4061802A (en) * 1966-10-24 1977-12-06 Costello Francis E Plating process and bath

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2806835A1 (de) * 1978-02-17 1979-08-23 Bayer Ag Metallisiertes papier
DE3411980A1 (de) * 1984-03-28 1985-10-10 Schering AG, Berlin und Bergkamen, 1000 Berlin Waessriges, stabiles bad zur chemischen abscheidung von kobalt-phosphor-nickel-phosphor- und kobalt-nickel-phosphor-legierungen

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1207218A (en) * 1914-01-19 1916-12-05 L Aluminium Francais Soc Process of producing metallic deposits.
US2532283A (en) * 1947-05-05 1950-12-05 Brenner Abner Nickel plating by chemical reduction
US2871142A (en) * 1955-05-20 1959-01-27 North American Aviation Inc Chemical nickel and cobalt plating process
US3024134A (en) * 1953-07-24 1962-03-06 Gen Motors Corp Nickel chemical reduction plating bath and method of using same
US3211578A (en) * 1961-11-27 1965-10-12 Gen Am Transport Chemical nickel plating of magnesium and its alloys
US3288639A (en) * 1962-05-31 1966-11-29 Xerox Corp Method for making a plural layered printed circuit board

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1207218A (en) * 1914-01-19 1916-12-05 L Aluminium Francais Soc Process of producing metallic deposits.
US2532283A (en) * 1947-05-05 1950-12-05 Brenner Abner Nickel plating by chemical reduction
US3024134A (en) * 1953-07-24 1962-03-06 Gen Motors Corp Nickel chemical reduction plating bath and method of using same
US2871142A (en) * 1955-05-20 1959-01-27 North American Aviation Inc Chemical nickel and cobalt plating process
US3211578A (en) * 1961-11-27 1965-10-12 Gen Am Transport Chemical nickel plating of magnesium and its alloys
US3288639A (en) * 1962-05-31 1966-11-29 Xerox Corp Method for making a plural layered printed circuit board

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4061802A (en) * 1966-10-24 1977-12-06 Costello Francis E Plating process and bath
US3962495A (en) * 1972-11-08 1976-06-08 Rca Corporation Method of making duplicates of optical or sound recordings

Also Published As

Publication number Publication date
GB1111258A (en) 1968-04-24
JPS4945209B1 (enExample) 1974-12-03
DE1621326A1 (de) 1971-05-13

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