Classifications

• • 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
  • C25D3/48—Electroplating: Baths therefor from solutions of gold

Definitions

• the present invention is based on the discovery that small amounts of thallium 'in' the-electrolytic solution employed within a defined pH range have a beneficial effect on the gold deposit, providing a plate of acceptable aesthetic qualities as well as one which is uniformly distributed and readily attachable to other surfaces.
• small amounts is meant not more than mg./l. and preferably between 3 to 50 milligrams of thallium per liter of plating solution.
• these limits should be observed since operation outside of this range and especially on the high side, yields gold deposits which are unsuitable in one or more of several respects, especially in attachability to other surfaces.
• Thegold present in the electrolytic solution of the present invention is added in the form of the gold-cyanide double salt of an alkali metal.
• an alkali metal typically, potassium or sodium gold-cyanide are employeds
• the bath may contain sufficient gold to perform under the conditions desired by the plater but ordinarily the amountpresent in the bath is suitably in the range of from 1 to 75 grams per liter and preferably 8 to l2 grams perliter.
• the electrolytic bath also contains sufficient conducting and buffering materials to give a pH in the range of at least 6.5 and preferably from about 7 to about 13.
• the advantages of the invention are best obtained from baths having a pH on the alkaline side, that is in the range of from about 10 to 12 and this constitutes the most preferred mode of the invention.
• the desired pI-I may be obtainedin a variety of ways known to those skilled in the art. For example, if the inherent pH of the bath is within the'desired range, then additional buffer materials need not be supplied. If, however, the pH is either too high or too low, appropriate acidic or basic materials can be added to reach the desired pH.
• inorganic acids such as hydrochloric 7 acid, hydrobromicacid, phosphoric acid and the like
• organic acids especially weak acids suchas formic acid, citric acid, acetic acid, tartaric acid, gluconic acid,.and the like. These may be employed singly or in combination. Additionally, they may be employed as partially'neutralized materials using alkaline reactants such as ammonium or alkali metal hydroxides and carbonates such as ammonium, sodium or potassium hydroxides,.ammonium carbonate and the like.
• vsoluble'thallous and thallic salts such as the sulfides, chlorides,
• the electrolytic solution may contain other materials as desired'such as conducting salts and the like, which may also act in the capacity of buffering materials.
• it is suitable'toprovide-one or more of the sulfate,-sulfamate, formate, acetate, citrate, lactate, tartrate,'fiuoroborate, borate,
• phosphate ions may be provided in theform'of asuitable metal-salt.
• suitable results are obtained at levels ranging from 10 to 500 g. of the salt per liter of plating solution.
• the desired pI-lin the bathis obtainedinherently from such materials it may be unnecessary to add additional buffering and conducting materials.
• the use of these salts, and others is desirable when an alloy of'electrodeposited gold is sought such as is obtained by adding from 0-100 g./l. of alum toproduce a 24 karat gold alloy.
• the electrolytic solutions of the present invention are utilizedin'theelectroplating process at current densities suitably in the'range of l to 200 and preferably 2 to 10 amperes per square foot.
• the temperature of operation is preferably elevated, of the order of 100 to 180 F. Higher or lower temperatures may be employed if desired. For example, temperatures in range of from 50 to 180 F. are suitable.
• EXAMPLE 1 A 24 karat gold plating electrolyte solution is formulated by dissolving the indicated materials in sufficient water to make 1 liter of solution.
• Gold [as KAu(CN),] 12 grams Na," P 60 grams Thallium (as TI,SO.) 20 milligrams The pH was adjusted to about 10.5.
• a header consisting of a cap having several small leads extending therefrom is plated at a temperature of around 140 F. at a current density of around 5 amps. per square foot.
• a smooth semibright 24 karat lemonyellow gold deposit is obtained on the header. The deposit is uniformly distributed over the cap and small wire leads of the transistor header.
• Example ll The procedure of Example 1 is followed utilizing an electrolyte made from the following materials in sufficient water to make 1 liter of solution.
• Gold [as KAu(CM ),l 24 grams Na,H P0 60 grams Trisodium citrate 60 grams Thallium (as T1 80 I40 milligrams The pH of the solution was adjusted to 10.0. The plating is conducted at a temperature of around 150 F. at a current density of around 6 amps. per square foot yielding a 24 karat lemon-yellow gold deposit. The deposit is smooth and semibright, has a uniform gold thickness and exhibits good characteristics of attachability to gold-silicon dies.
• Example 1 The procedure of Example 1 is followed utilizing an electrolyte made from the following materials in sufficient water to make 1 liter of solution.
• Example IV The procedure of Example I is followed utilizing an electrolyte made from the following materials in sufficient water to make 1 liter of solution.
• An aqueous electrolytic cyanide-gold plating solution comprising a gold cyanide complex, from 1 to 140 milligrams of thallium per liter of plating solution and sufficient conducting and buffering materials to provide a pH in said solution of at least 6.5.
• conducting and buffering compounds comprise ammonium hydroxide, potassium hydroxide, sodium hydroxide or ammonium carbonate.

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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)

Applications Claiming Priority (1)

Publications (1)

Family

ID=21968602

Family Applications (1)

Country Status (13)

Cited By (4)

Families Citing this family (2)

• 1970
  • 1970-06-29 US US50969A patent/US3644184A/en not_active Expired - Lifetime
• 1971
  • 1971-06-11 CH CH859571A patent/CH525963A/fr not_active IP Right Cessation
  • 1971-06-16 GB GB2811771A patent/GB1349796A/en not_active Expired
  • 1971-06-23 DE DE19712131815 patent/DE2131815A1/de not_active Withdrawn
  • 1971-06-23 BE BE768886A patent/BE768886A/xx not_active IP Right Cessation
  • 1971-06-24 SE SE08283/71A patent/SE360888B/xx unknown
  • 1971-06-26 ES ES392679A patent/ES392679A1/es not_active Expired
  • 1971-06-28 DK DK316771AA patent/DK133791B/da unknown
  • 1971-06-28 AT AT05592/71A patent/AT313663B/de not_active IP Right Cessation
  • 1971-06-28 NL NL717108893A patent/NL149861B/xx not_active IP Right Cessation
  • 1971-06-29 JP JP4757871A patent/JPS5534235B1/ja active Pending
  • 1971-06-29 CA CA116933A patent/CA929481A/en not_active Expired
  • 1971-06-29 FR FR7124926*A patent/FR2096799B1/fr not_active Expired

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