US3235392A - Electroless deposition of palladium - Google Patents

Electroless deposition of palladium Download PDF

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Publication number
US3235392A
US3235392A US143577A US14357761A US3235392A US 3235392 A US3235392 A US 3235392A US 143577 A US143577 A US 143577A US 14357761 A US14357761 A US 14357761A US 3235392 A US3235392 A US 3235392A
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Prior art keywords
palladium
acid
dinitrito
aqueous solution
deposition
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US143577A
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Miles John Joseph
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Automatic Telephone and Electric Co Ltd
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Automatic Telephone and Electric Co Ltd
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Priority claimed from GB3096261A external-priority patent/GB988174A/en
Priority claimed from GB3476460A external-priority patent/GB958685A/en
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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
    • C23C18/42—Coating with noble metals
    • C23C18/44—Coating with noble metals 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
    • C23C18/42—Coating with noble metals

Definitions

  • the deposition of metals by electroless or chemical techniques involves the simple chemical formation of the desired metal by interaction of the components of the plating bath used,'followed by deposition of such metal upon articles immersed in the bath.
  • Known chemical plating baths suffer from certain disadvantages. For instance, acid-type baths tend to remove zinc from brass articles upon which a deposit is to be made, which adversely affects the quality of the resultant plated coating. Alkalitype baths are unstable and are liable to sufier spontaneous decomposition.
  • a more specific object of the invention is to provide novel palladium compounds for use in such baths and also to provide baths which give adherent smooth bright deposits on a variety of metallic supports or basis metals and which avoid dezincification of brass articles.
  • a chemical plating bath for the electroless plating of palladium comprises an aqueous solution containing a source of palladium ions in complexed form and a source of sulphamate ions, the aqueous solution having a pH in the range of 1.0 to 3.5.
  • the palladium is present in the plating bath as a sulphamate complex thereof.
  • the proposed bath is essentially an acid solution of palladium complexed as sulphamate, sulphate, diamminosulphamate, diammino-sulphate, dinitrito-disulphamato or other palladium complexes, which deposits palladium on to suitable metallic surfaces by simple immersion.
  • the preferred concentration of the metal in the bath is 1 to 100 g./l.
  • the deposits are adherent, smooth and bright and atlord a high degree of protection against normal atmospheric corrosion. Satisfactory deposits can be obtained on copper, copper alloys, nickel, silver, germanium, steel and aluminium.
  • a typical bath in gms. per litre consists of:
  • Palladium (as metal) Palladium sulphamate 30 Sulphamic acid about 10
  • a pH range of 1.5 to 2.5 is suitable, that is, a pH in the lower portion of the aforementioned overall range of 1.0 to 3.5; for less reactive metals than copper and its alloys, such as nickel and silver, an even lower pH range of 1.0 to 2.0 is suitable; for more reactive metals such as aluminium and steel, a pH range of 2.5 to 3.5 is preferred, namely, in the upper portion of the overall range.
  • the solution is contained in non-reactive vessels such as glass or polyethylene. Since the rate of deposition is a function of temperature, the solution may require to be heated.
  • Inch palladium per hr. At 20 C. 0.00003 At C. 0.00016
  • the articles to be plated are cleaned in a suitable manner, i.e. as for conventional electroplating, and preferably rinsed in deionized water prior to immersion in the plating bath.
  • Example I 25 gms. of palladium diammino-dinitrite salt were added slowly, i.e. about 5 gms. at a time, to ml. of an aqueous solution containing 20 gms. sulphamic acid at about 50 C. A vigorous reaction occurred with evolution of nitrogen. When dissolution was complete, the solution was brought rapidly to the boil and then cooled quickly to 50 C. and maintained at that temperature for 4 hours, taking care to prevent loss of volume by evaporation. The volume was adjusted to 1 litre, which contained 10 gms. of metallic palladium as the diamminodisulphamate.
  • a piece of copper was cleaned in the conventional manner for subsequent electroplating and immersed in the solution prepared as above.
  • Deposition of palladium took place immediately by ionic replacement, which process gradually becomes supplanted by What appears to be auto-catalytic deposition of palladium, which proceeds indefinitely or until the piece is withdrawn.
  • a thickness of 0.00001 inch of palladium is obtained in 15 minutes, this being largely achieved by replacement. In 60 minutes a thickness of 0.00003 inch is obtained, the increase in thickness being due to auto-catalytic reduction.
  • the coatings are smooth, bright and adherent.
  • Example 2 13 gms. of palladous hydroxide, prepared as described in co-pending application Serial No. 204,627, filed June 22, 1962, were added slowly, in 5 gm. portions, to 100 mls. of an aqueous solution containing 20 gms. of sulphamic acid at about 50 C. The solution was treated as described in Example 1 and used for the electroless plating of copper, with substantially the same results.
  • Example 3 A solution containing 20 gms. palladium per litre was prepared as described in Example 1, the ratio of sulphamic acid to metallic palladium content being maintained in the ratio of 2 to 1.
  • Example 4 A solution containing 30 gms. palladium per litre was prepared as described in Example 1, the ratio of sulphamic acid to metallic palladium content being maintained in the ratio of 2 to 1.
  • sulphamic acid in a concentration sufficient to maintain the pH of the aqueous solution in the range of 1.0 to 3.5.
  • a method of electrolessly plating palladium onto an article having a metal surface which consists essentially in at least partially immersing an article having a metal surface in a chemical plating bath consisting of an aqueous solution containing (1).
  • a source of ions of palladium in complexed form in an amount of from 1 to 100 g./l.
  • said source being selected from the group consisting of palladium diamminodisulphamate, palladium diammino-sulphate, ammonium disulphamato-dinitrito-palladite, ammonium sulphate-dinitrito-palladite, disulphamato-dinitrito-palladous acid and sulphato-dinitrito-palladous acid and (2) sulphamic acid in a concentration sufficient to maintain the pH of the aqueous solution in the range of 1.0 to 3.5.

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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)

Description

United States Patent 3,235,392 ELECTROLESS DEPOSITION OF PALLADIUM .lohn Joseph Miles, Liverpool, England, assignor to Automatic Telephone & Electric Company Limited, Liverpool, England, a British company No Drawing. Filed Oct. 9, 1961, Ser. No. 143,577 Claims priority, application Great Britain, Oct. 11, 1960, 34,764/ 60 2 Claims. (Cl. 106-1) This invention relates to electroless plating or chemical plating, that is to say, to the deposition of metals without electrolysis, and is concerned, in particular, with the electroless deposition of palladium.
In comparison with electrolytic plating methods, the deposition of metals by electroless or chemical techniques involves the simple chemical formation of the desired metal by interaction of the components of the plating bath used,'followed by deposition of such metal upon articles immersed in the bath. Known chemical plating baths suffer from certain disadvantages. For instance, acid-type baths tend to remove zinc from brass articles upon which a deposit is to be made, which adversely affects the quality of the resultant plated coating. Alkalitype baths are unstable and are liable to sufier spontaneous decomposition.
It is an object of the present invention to provide improved chemical plating baths for the deposition of palladium. A more specific object of the invention is to provide novel palladium compounds for use in such baths and also to provide baths which give adherent smooth bright deposits on a variety of metallic supports or basis metals and which avoid dezincification of brass articles.
According to the invention, a chemical plating bath for the electroless plating of palladium comprises an aqueous solution containing a source of palladium ions in complexed form and a source of sulphamate ions, the aqueous solution having a pH in the range of 1.0 to 3.5.
Preferably, the palladium is present in the plating bath as a sulphamate complex thereof.
The proposed bath is essentially an acid solution of palladium complexed as sulphamate, sulphate, diamminosulphamate, diammino-sulphate, dinitrito-disulphamato or other palladium complexes, which deposits palladium on to suitable metallic surfaces by simple immersion. The preferred concentration of the metal in the bath is 1 to 100 g./l.
It is essential that there be free sulphamic ions present, the concentration being such as to maintain the pH in the desired range.
One of the advantages of the proposed bath is that, on brass alloys, dezincification is negligible and the quality of the coating is thus improved.
The deposits are adherent, smooth and bright and atlord a high degree of protection against normal atmospheric corrosion. Satisfactory deposits can be obtained on copper, copper alloys, nickel, silver, germanium, steel and aluminium.
A typical bath in gms. per litre consists of:
Palladium (as metal) Palladium sulphamate 30 Sulphamic acid, about 10 For copper and its alloys, a pH range of 1.5 to 2.5 is suitable, that is, a pH in the lower portion of the aforementioned overall range of 1.0 to 3.5; for less reactive metals than copper and its alloys, such as nickel and silver, an even lower pH range of 1.0 to 2.0 is suitable; for more reactive metals such as aluminium and steel, a pH range of 2.5 to 3.5 is preferred, namely, in the upper portion of the overall range.
ice
The solution is contained in non-reactive vessels such as glass or polyethylene. Since the rate of deposition is a function of temperature, the solution may require to be heated.
Typical rates of deposition on copper using the above solution are:
Inch palladium per hr. At 20 C. 0.00003 At C. 0.00016 The articles to be plated are cleaned in a suitable manner, i.e. as for conventional electroplating, and preferably rinsed in deionized water prior to immersion in the plating bath.
Deposition takes place immediately on immersion and ceases on withdrawal. This means that the solution is stable and, provided dust and foreign matter are excluded, no loss of palladium is experienced from spontaneous decomposition.
Thin, protective deposits of palladium are readily obtainable on printed circuits, connector springs, plug and socket components. Silver and silver-plated articles can be given a cheap non-tarnishable finish. Germanium can be readily given a deposit of palladium to facilitate electrical connections thereto.
In order that the invention may be readily understood, the following specific examples are given by way of illustration.
Example I 25 gms. of palladium diammino-dinitrite salt were added slowly, i.e. about 5 gms. at a time, to ml. of an aqueous solution containing 20 gms. sulphamic acid at about 50 C. A vigorous reaction occurred with evolution of nitrogen. When dissolution was complete, the solution was brought rapidly to the boil and then cooled quickly to 50 C. and maintained at that temperature for 4 hours, taking care to prevent loss of volume by evaporation. The volume was adjusted to 1 litre, which contained 10 gms. of metallic palladium as the diamminodisulphamate.
A piece of copper was cleaned in the conventional manner for subsequent electroplating and immersed in the solution prepared as above. Deposition of palladium took place immediately by ionic replacement, which process gradually becomes supplanted by What appears to be auto-catalytic deposition of palladium, which proceeds indefinitely or until the piece is withdrawn.
At room temperature, a thickness of 0.00001 inch of palladium is obtained in 15 minutes, this being largely achieved by replacement. In 60 minutes a thickness of 0.00003 inch is obtained, the increase in thickness being due to auto-catalytic reduction. The coatings are smooth, bright and adherent.
Example 2 13 gms. of palladous hydroxide, prepared as described in co-pending application Serial No. 204,627, filed June 22, 1962, were added slowly, in 5 gm. portions, to 100 mls. of an aqueous solution containing 20 gms. of sulphamic acid at about 50 C. The solution was treated as described in Example 1 and used for the electroless plating of copper, with substantially the same results.
Example 3 A solution containing 20 gms. palladium per litre was prepared as described in Example 1, the ratio of sulphamic acid to metallic palladium content being maintained in the ratio of 2 to 1.
After suitable cleaning, a piece of copper alloy was immersed in this solution for 60 mins. at a temperature 3 of 50 C. A smooth, adherent coating of palladium about 0.00006 inch was obtained.
Example 4 A solution containing 30 gms. palladium per litre was prepared as described in Example 1, the ratio of sulphamic acid to metallic palladium content being maintained in the ratio of 2 to 1.
A piece of copper alloy, immersed for 60 mins. after suitable cleaning, gave the following thicknesses of palladium as a smooth, adherent coating:
Inch
At 20 C. 0.00012 At 50 C. 0.0002
At 75 C. 0.0004
I claim:
sulphamic acid in a concentration sufficient to maintain the pH of the aqueous solution in the range of 1.0 to 3.5.
2. A method of electrolessly plating palladium onto an article having a metal surface, which consists essentially in at least partially immersing an article having a metal surface in a chemical plating bath consisting of an aqueous solution containing (1). a source of ions of palladium in complexed form in an amount of from 1 to 100 g./l. of palladium as metal, said source being selected from the group consisting of palladium diamminodisulphamate, palladium diammino-sulphate, ammonium disulphamato-dinitrito-palladite, ammonium sulphate-dinitrito-palladite, disulphamato-dinitrito-palladous acid and sulphato-dinitrito-palladous acid and (2) sulphamic acid in a concentration sufficient to maintain the pH of the aqueous solution in the range of 1.0 to 3.5.
References Cited by the Examiner UNITED STATES PATENTS 2,361,203 10/1944 Holdaway et al. 20446 XR 2,458,839 1/1949 Dyer 117130 2,720,494 10/1955 Suter et al. 20447 2,984,604 5/1961 Duva et al. 20447 ALEXANDER H. BRODMERKEL, Primary Examiner.
JOSEPH REBOLD, MORRIS LIEBMAN, Examiners.

Claims (1)

1. A CHEMICAL PLATING BATH FOR THE ELECTROLESS PLATING OF PALLADIUM ON A METAL SURFACE, WHICH CONSISTS ESSENTIALLY OF AN AQUEOUS SOLUTION CONTAINING (1) A SOURCE OF IONS OF PALLADIUM IN COMPLEXED FORM IN AN AMOUNT OF FROM 1 TO 100 G./L. OF PALLADIUM AS METAL, SAID SOURCE BEING SELECTED FROM THE GROUP CONSISTING OF PALLADIUM DIAMMINO-DISULPHAMATE, PALLADIUM DIAMMINO-SULPHATE, AMMONIUM DISULPHAMATO-DINITRITO-PALLADITE, SMMONIUM SULPHATO-DINITRITO-PALLADITE, DISULPHAMATO-DINITRO-PALLADOUS ACID AND SULPHATO-DINITRITO-PALLADOUS ACID AND (2) SULPHAMIC ACID IN A CONCENTRATION SUFFICIENT TO MAINTAIN THE PH OF THE AQUEOUS SOLUTION IN THE RANGE OF 1.0 TO 3.5.
US143577A 1960-10-11 1961-10-09 Electroless deposition of palladium Expired - Lifetime US3235392A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB3096261A GB988174A (en) 1960-10-11 1960-10-11 Improvements in or relating to the plating of palladium and other metals of group viii
GB3476460A GB958685A (en) 1960-10-11 1960-10-11 Improvements in or relating to palladium plating

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3345158A (en) * 1964-08-10 1967-10-03 Ibm Electrical conductor material and method of making same
US3530050A (en) * 1964-06-12 1970-09-22 Johnson Matthey Co Ltd Electrodeposition of palladium
US3915350A (en) * 1973-03-05 1975-10-28 Colonial Metals Inc Catalytic mixture and method of use therefor
US5264288A (en) * 1992-10-01 1993-11-23 Ppg Industries, Inc. Electroless process using silylated polyamine-noble metal complexes
US5773096A (en) * 1993-10-29 1998-06-30 General Electric Company Method of catalyst preparation by high-temperature hydrothermal incorporation of noble metals onto surfaces and matrices
US5818893A (en) * 1993-10-29 1998-10-06 General Electric Company In-situ palladium doping or coating of stainless steel surfaces
US20050167281A1 (en) * 2004-01-30 2005-08-04 Tetsuya Ohsawa Production method of suspension board with circuit

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2361203A (en) * 1942-01-01 1944-10-24 Bell Telephone Labor Inc Electron discharge device and method of manufacture
US2458839A (en) * 1944-04-19 1949-01-11 Indium Corp America Electrodeposition of indium and its alloys
US2720494A (en) * 1950-01-09 1955-10-11 Harold R Suter Process of preparing catalytic elements
US2984604A (en) * 1958-08-06 1961-05-16 Sel Rex Corp Platinum plating composition and process

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2361203A (en) * 1942-01-01 1944-10-24 Bell Telephone Labor Inc Electron discharge device and method of manufacture
US2458839A (en) * 1944-04-19 1949-01-11 Indium Corp America Electrodeposition of indium and its alloys
US2720494A (en) * 1950-01-09 1955-10-11 Harold R Suter Process of preparing catalytic elements
US2984604A (en) * 1958-08-06 1961-05-16 Sel Rex Corp Platinum plating composition and process

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3530050A (en) * 1964-06-12 1970-09-22 Johnson Matthey Co Ltd Electrodeposition of palladium
US3345158A (en) * 1964-08-10 1967-10-03 Ibm Electrical conductor material and method of making same
US3915350A (en) * 1973-03-05 1975-10-28 Colonial Metals Inc Catalytic mixture and method of use therefor
US5264288A (en) * 1992-10-01 1993-11-23 Ppg Industries, Inc. Electroless process using silylated polyamine-noble metal complexes
US5773096A (en) * 1993-10-29 1998-06-30 General Electric Company Method of catalyst preparation by high-temperature hydrothermal incorporation of noble metals onto surfaces and matrices
US5818893A (en) * 1993-10-29 1998-10-06 General Electric Company In-situ palladium doping or coating of stainless steel surfaces
US20050167281A1 (en) * 2004-01-30 2005-08-04 Tetsuya Ohsawa Production method of suspension board with circuit

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