Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/02—Contacts characterised by the material thereof
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
  • H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts
  • H01H11/041—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts by bonding of a contact marking face to a contact body portion
  • H01H2011/046—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts by bonding of a contact marking face to a contact body portion by plating
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49002—Electrical device making
  • Y10T29/49117—Conductor or circuit manufacturing
  • Y10T29/49204—Contact or terminal manufacturing
  • Y10T29/49224—Contact or terminal manufacturing with coating

Definitions

• the palladium is electrodeposited from an aqueous ammoniacal bath comprising tetrammino-palladous bromide and having a pH of about 8-10.
• the resulting palladium deposit is highly ductile and thus permits subsequent deformation of the coated article to form electrical contacts.
• the present invention is directed to a method for producing palladium electrodeposits of high ductility and, more particularly, to the provision of electrical contacts made of a ductile metal having thereon a surface coating of ductile palladium.
• the coatings are conveniently formed by electro-deposition from aqueous baths but it is a disadvantage of palladium coatings electrodeposited from commercially available baths that they exhibit high internal stress and low ductility and have a tendency to crack if the coating is thick. Even if a stressed coating is free of cracks when initially deposited, it may develop cracks in service if its ductility is low, Cracking of the coating reduces the protection it affords against corrosion.
• palladium coatings on electrical contacts are formed by the electrodeposition of palladium from a bath consisting of an aqueous ammoniacal solution of tetramminopalladous bromide, (Pd (NH )Br and this invention includes coated contacts so produced.
• Pd (NH )Br tetramminopalladous bromide
• This invention includes coated contacts so produced.
• coatings have remarkably high ductility and are wholly or substantially wholly free from cracks as determined by an electrographic test at thicknesses even as great as 10 microns or more. Moreover, at thicknesses even as low as 2 microns, the protection afforded by the coating is very good.
• the electrographic test referred to comprises placing a sheet of cadmium sulfide paper with a moistened backing pad against a plated specimen and making the specimen anodic.
• Blackening of the cadmium sulfide paper occurs at the pores and cracks.
• the bath advantageously contains from 15 to 30 grams per liter (g.p.l.) of palladium as tetramminopalladous bromide, and has a pH of from 8 to 9.
• g.p.l. grams per liter
• the bath advantageously contains from 15 to 30 grams per liter (g.p.l.) of palladium as tetramminopalladous bromide, and has a pH of from 8 to 9.
• Higher or lower palladium concentrations may, however, be used and, broadly speaking, the palladium content may be from 2 to 35 g.p.l. With low palladium concentrations below about 15 g.p.l., only a narrow range of current densities can be employed while still obtaining high ductility in the deposits and it is for this reason that palladium concentrations of 15 g.p.l, and higher are advantageously employed.
• the pH of the bath is quite critical.
• the bath is operative in the diaphragm cell at a pH up to 10 provided that ammonia is continuously added to the bath.
• the ammonia concentration of the bath may be 20 to 70 g.p.l. expressed as ammonium bromide, with advantageous results being obtained using 50 to 60 g.p.l. ammonium bromide.
• the efiiciency of the bath and the ductility of the deposits falls as the cathode current density is increased above 2.0 amperes per square decimeter, and the current density is advantageously not more than 1.5 amperes per square decimeter to obtain best efliciency and ductility.
• Deposition proceeds at a satisfactory rate at room temperature when the cathode current density is at least '0.5 ampere per square decimeter, or advantageously, at
• the bath may be operated in the temperature range of about 18 C. to about 60 C.
• the bath is preferably employed as the catholyte in a cell divided into cathode and anode compartments by a porous diaphragm, the electrolyte in the anode compartment conveniently being composed of ammonium carbonate, ammonium sulfate and ammonia.
• Insoluble anodes for example, of platinum, are used.
• the bath solution does not attack any of the common base metals and the substrate on which the palladium is supported may consist, for example, of a ductile metal such as copper, brass, beryllium-copper, nickel or nickelsilver.
• the bath may conveniently be prepared by dissolving palladium sponge in.'an excess of concentrated aqueous hydrobromic acid, with the addition of small amounts of bromine to promote solution, and evaporating the resulting solution to dryness to remove excess hydrobromic acid and reduce any tetravalent palladium to the divalent state.
• the dry palladium bromide thus obtained is dissolved in the minimum amount of dilute hydrobromic acid.
• Ammonia is added and the solution heated until the precipitate first formed just redissolves.
• the solution is filtered and diluted as required.
• a bath was prepared by dissolving 15 grams of palladium in 150 milliliters concentrated hydrobromic acid and warming with small additions of bromine till all the palladium was dissolved. The solution was evaporated to dryness to give palladium bromide, which was dissolved in approximately milliliters of hot 50% hydrobromic acid. The clear solution was treated with approximately milliliters of ammonia and diluted to 1 liter. The resulting bath continued 15 g.p.l. of palladium and had a pH of 8.5. It was used at room temperature in the cathode compartment of a diaphragm cell with anodes of palladium and an anolyte consisting of an aqueous solution of 20 g.p.l.
• ammonium sulfate 10 g.p.l. ammonium carbonate and 50 milliliters per liter ammonia (s.g. 0.88)
• s.g. 0.88 milliliters per liter ammonia
• the deposit was smooth, had a hardness of 187 D.P.N., a stress of 10 long tons per square inch tensile and was so ductile that it had anelongation of 14%.
• the deposit was essentially crack-free.
• An identical bath used in a single-compartment cell with anodes in the electrolyte had a very limited life, owing to sludging, but deposits of ductility as high as 20% could be obtained from it.
• the improved ductility and lower hardness of the deposits obtained in accordance with the invention are shown by the following table, in which their properties are compared with those of deposits from similar chloride and sul- Eate baths and also of a deposit from a commercial bath consisting of an ammoniacal solution of tetramminopalladous nitrate. In each of the solutions, the concentration of palladium was within the range of 10 to 20 g.p.l. The substrate material was copper.
• coatings were obtained from at least two similar electrolytes. Hardness and ductility were measured on different specimens. The ductility was measured on specimens having a coating microns thick and the hardness on specimens having a coating microns thick.
• Palladium deposits formed from similar ammoniacal solutions of tetramminopalladous phosphate, nitrate, tartrate, citrate, oxalate and carbonate are unsatisfactory for use on electrical contacts, since they fail to give useful protection to the basis metal within the thickness range of 2 to 10 microns.
• Tetramminopalladous iodide solutions decompose spontaneously and are therefore useless.
• Palladium-plated electrical contacts according to the invention are particularly useful for the spring components of plug-and-socket contacts, which often have to withstand severe deformation on crimping, as well as repeated flexing during insertion and withdrawal in service.
• the high ductility of the coatings makes it possible to employ much thicker coatings than hitherto, thereby increasing protection. Coatings 8 microns thick have proved satisfactory. If desired, however, the coatings can be built to greater thicknesses, e.g., 30 microns.
• the improvement which comprises electrodepositing ductile palladium upon such a component made of a ductile metal from the group consisting of copper, brass, beryllium-copper, nickel, and nickel-silver immersed as a cathode in a diaphragm cell provided in the cathode compartment thereof with an aqueous ammoniacal bath containing about 2 to about 35 grams per liter of palladium as tetramminopalladous bromide and having a pH of about 8 to about 10 using a cathode current density of about 0.5 to about 2 amperes per square decimeter to provide a palladium coating at least about 2 microns thick upon said component and thereafter deforming said plated component to produce an electrical contact.
• a ductile metal from the group consisting of copper, brass, beryllium-copper, nickel, and nickel-silver immersed as a cathode in a diaphragm cell provided in the cathode compartment thereof with an aque

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Electroplating Methods And Accessories (AREA)
• Paints Or Removers (AREA)

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Citations (3)

• 0
  • NL NL130012D patent/NL130012C/xx active
• 1965
  • 1965-03-09 GB GB9957/65A patent/GB1062681A/en not_active Expired
• 1966
  • 1966-03-01 US US530777A patent/US3500537A/en not_active Expired - Lifetime
  • 1966-03-05 DE DEJ30234A patent/DE1262722B/de active Pending
  • 1966-03-08 FR FR52579A patent/FR1473425A/fr not_active Expired
  • 1966-03-08 ES ES0323939A patent/ES323939A1/es not_active Expired
  • 1966-03-09 CH CH335866A patent/CH441921A/fr unknown
  • 1966-03-09 JP JP1457666A patent/JPS444891B1/ja active Pending
  • 1966-03-09 BE BE677564D patent/BE677564A/xx unknown
  • 1966-03-09 NL NL6603087A patent/NL6603087A/xx unknown
  • 1966-10-17 US US586937A patent/US3544435A/en not_active Expired - Lifetime

Patent Citations (3)

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