US3427231A - Method of electroplating and electroforming gold in an ultrasonic field - Google Patents

Method of electroplating and electroforming gold in an ultrasonic field Download PDF

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Publication number
US3427231A
US3427231A US473746A US3427231DA US3427231A US 3427231 A US3427231 A US 3427231A US 473746 A US473746 A US 473746A US 3427231D A US3427231D A US 3427231DA US 3427231 A US3427231 A US 3427231A
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Prior art keywords
gold
plating
solution
cyanide
ultrasonic
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Expired - Lifetime
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US473746A
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English (en)
Inventor
Edward B Schneider
Melvin E Lindell
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Northrop Grumman Guidance and Electronics Co Inc
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Litton Systems Inc
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/20—Electroplating using ultrasonics, vibrations
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/627—Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance
    • 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
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/922—Static electricity metal bleed-off metallic stock
    • Y10S428/9335—Product by special process
    • Y10S428/934—Electrical process
    • Y10S428/935—Electroplating
    • 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
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12861—Group VIII or IB metal-base component
    • Y10T428/12889—Au-base component

Definitions

  • This invention pertains to a method for electroplating substantially pure gold onto a basis metal, to a novel electrolytic bath used in that plating, and to a method for electroplating said gold in the presence of an ultrasonic field.
  • the gold which is plated is exceptionally pure, uniform, and dense.
  • the method may also be used for electroforming.
  • Gold plate may be electro deposited, in accordance with this invention, with a purity of a Type I plate and a hardness equal to or better than a Type II plate as those types are defined in Military Specification MILG45204, dated Mar. 7, 1960, and set forth in the Metal Finishing Directory Guidebook for 1965, published by Metals &
  • a novel gold plating bath is placed in an ultrasonic field which prevents polarization at the electrodes, allows exceptionally high current densities to be used, and substantially increases the throwing power of the plating solution to cause the electroplated gold to be uniformly distributed over the basis metal, to cause the plated gold to be exceedingly pure, to cause the plated gold to be exceptionally dense, and to cause the gold to deposit at an exceptionally rapid rate.
  • the metallurgical structure of the plated gold assumed a novel configuration, hereinafter designated as laminar gold plate.
  • the process of this invention uses an ultrasonic generator and transducer in combination with a plating solution.
  • the plating solution is composed of alkali gold double cyanide salt in water which is heated, for example, to 150 F. to keep the required amount of alkali gold double cyanide in solution.
  • a typical alkaline gold double cyanide plating bath of the prior art has a gold concentration of 1 to 2 troy ounces of gold per gallon of plating bath.
  • the plating bath of this invention uses over 5 troy ounces of gold (in the form of an alkali gold double cyanide) per gallon of plating solution, with a preferred range of 7 to 9 troy ounces of gold at 150 F.
  • the upper limit of the amount of gold which is useful is determined by the saturation constant of the alkali gold double cyanide in the plating solution at the elevated temperature in the presence of an ultrasonic field.
  • prior known acid-type gold plating baths or solution operate in the range of to 160 F.
  • prior known alkaline gold plating baths or solutions normally are used below 130 F. because in the use of the prior art alkaline baths the gold plate becomes softer when plated at higher temperatures.
  • the plating solution temperature may be increased to boiling. Because the purpose of increasing the temperature i to allow a greater concentration of gold to be placed into solution, F. is typical for this invention. At higher temperatures additional gold may be placed into solution.
  • potassium cyanide and/ or sodium cyanide may be added to increase the conductivity and throwing power of the solution.
  • sodium cyanide is used, brightness is increased directly as a function of the amount of free sodium ion which is added. Hardness and throwing power are also increased.
  • the usual current density range for plating gold in accordance with the prior art, is between 2 and 10 amperes per square foot. Any increase beyond that range causes a polarization at the electrodes with resultant deterioration in the plate quality.
  • the plating current may be increased indefinitely. Typically, plating current densities between 30 and 50 amperes per square foot are used. It is possible, however, to use plating currents, for example, of the order of 1000 amperes per square foot.
  • the plating bath of this invention does not require a continuous filtration to remove the contaminants in order to produce substantially pure deposits of gold.
  • the pH of the plating solution does not vary, but remains substantially constant whereby the quality and characteristics of the plated gold is substantially constant from plated piece to plated piece.
  • the gold plate in accordance with this invention is substantially 24 karat or 100% pure gold produced from a plating solution which contains only the alkali earth metals and gold as the metallic ion. Gold purity exceeding 99.999% has been observed.
  • the gold plating bath of this invention together with the ultrasonics in accordance with this invention produces a gold plate which neither needs to be burnished nor polished, nor scratched to yield a bright finish.
  • the plating solution of this invention when used in accordance with the process of this invention, may yield bright electroplated gold even when the plate is a very heavy deposit, for example in excess of 0.0100 inch.
  • the gold is further brightened by the ultrasonic agitation of the plating solution itself.
  • the gold deposit produced in accordance with this in-' vention is dimensionally uniform and accurately reflects the machining tolerances of the basis metal. For example, reflection of the machining tolerances of the basis metal have been observed to an accuracy of 500 millionths of an inch.
  • the bath or plating solution of this invention does not use organic materials, it does not require aging before use.
  • the plating rate of the gold bath or solution of this invention in the process of ultrasonics varies over Wide ranges. For example, it has been observed that the plating rate may vary between 0.0002 inch per hour to a preferred rate of substantially 0.0001 inch per minute to a higher rate of 0.001 inch per minute.
  • the rate of deposition is a function of the plating current density.
  • the hardness of the plate is also a function of the plating current density (corresponding to rate of deposition) varying from a Knoop hardness of 125 to 220 with a corresponding current density range between approximately and 1000 amperes per square foot.
  • Knoop hardness is a microhardness determined from the resistance of metal to indentation by a pyramidal diamond indenter, having edge angles of 172 30' and 130, making a rhombohedral impression with one long and one short diagonal.
  • Knoop hardness (14230) (load in grams) (length of the longer diagonal, in microns) Further, because of the high rate of deposition available, electroforming of gold is practical with the process of this invention.
  • a direct result of the high density gold plate produced by the process of this invention is that a re-solderable condition is obtained, i.e. if one solders to the plate produced by said process with any of the well-known solder materials and then wishes to remove what has been soldered and later re-solder the same area, sutficient gold remains for solderability because with the dense gold deposit of this invention only half as much gold goes into solution the first time with the solder.
  • the required thickness for corrosion resistance of the basis metal can be greatly reduced.
  • the solution must be maintained basic, i.e. the pH of the solution is preferably in the alkaline range between 8.0 and 14.0 with an optimum range between 10.5 and 11.5 for brightness and smoothness.
  • a typical plating bath of this invention uses 7 to 9 troy ounces of gold (in the form of potassium gold double cyanide) per gallon of plating solution. If free potassium cyanide is added, between 3.6 ounces and 6 ounces of cyanide ion per gallon of solution is a typical concentration. If instead of potassium cyanide, free sodium cyanide is added, up to 2 ounces per gallon may be used. Either potassium cyanide or sodium cyanide increases the conductivity of the bath, adjusts the pH of the bath, and increases the leveling of the plate. The sodium cyanide also increases the throwing power and the hardness of the plate.
  • carbonates and Rochelle salts may be added if desired.
  • wetting agent such as pentadecafiuoro-octanoic acid up to 0.1% by Weight.
  • sodium laural sulfonate may be used as a wetting agent but these wetting agents are not necessary.
  • the minimum plating current density that can be used is that current density at which plating occurs without being pulled off by the ultrasonic cavitation. With an ultrasonic field intensity between 7 and 10 watts per square inch, the minimum plating current density which can be used is of the order of 15 amperes per square foot. With an ultrasonic field intensity of between 2.5 and 5 watts per square inch, the minimum plating current density is about 10 amperes per square foot. To characterize it differently, the cavitation created by the ultrasonic field prevents the metal ions from reaching the cathode unless the plating current density exceeds a predetermined minimum value.
  • the plating bath efiiciency increases as the frequency of the applied ultrasonics decreases until some critical frequency in the audio range is reached, after which the efficiency decreases rapidly.
  • the frequency which is used it is usually desirable that the frequency which is used be above the audible range of operators of the equipment. Accordingly, a frequency of the order of 20 kilocycles for the ultrasonics is typical.
  • the metallographic section of the plate has closely substantially uniformly spaced cells as shown in FIGS. 3 and 4.
  • FIGS. 3 and 4 where the plating current density was approximately 50 amperes per square foot, a laminar gold plate was found, i.e. the cells were flattened to cause the cell boundaries to be substantially parallel to the basis metal in a laminar pattern.
  • the plated pure gold has a Knoop hardness of over which means that it is a Type I gold in a Type II hardness range.
  • the amount of gold in solution should be decreased.
  • the amount of gold is increased and the throwing power of the gold is also increased.
  • FIGURE 1 is a partly schematic and partly structural view of a typical plating tank containing the plating bath of this invention and using an ultrasonic generator to generate an ultrasonic field to practice the process of this invention;
  • FIGURE 2 is a sketch of a metallographic view, magnified 1500 X, of a section of gold plated in an acid bath in accordance with the prior art;
  • FIGURE 3 is a sketch of a metallographic section, magnified 1500X, of gold plated in accordance with this invention at 30 amperes per square foot, and showing a columnar grain structure;
  • FIGURE 4 is a sketch of a metallographic section, magnified 1500 of gold plated, in accordance with this invention, at 50 amperes per square foot, and showing a laminar gold plate structure.
  • an ultrasonic transducer 12 which is preferably symmetrically placed with respect to the electrodes 20 and 22, is driven by an ultrasonic generator 14 and power amplifier 16.
  • the plating solution 18 of this invention is then agitated by the ultrasonic waves produced by transducer 12.
  • the efficiency of the plating increases as the frequency of the ultrasonic generator is reduced until, as some very low frequency, the eificiency suddenly drops off.
  • the frequency of the ultrasonic generator reaches the audible range, it becomes annoying to the operator.
  • a lowest inaudible frequency is desired.
  • ultrasonic generators which are used in ultrasonic cleaning, and the like have a frequency of approximately 20 kilocycles. A 20 kilocycle ultrasonic generator operates satisfactorily in the process of this invention.
  • a cathode 20 and an anode 22 are submerged, during plating, in the plating solution 18 with the item being plated at the cathode.
  • Plating current is supplied by a plating current supply 24, preferably at a rate above ten amperes per square foot.
  • the anode is annular about the cathode.
  • a mechanical agitator 26 is mechanically connected to the cathode 20 by a linkage 28.
  • the transducer 12 excites another liquid 183, such as water.
  • the plating tank is immersed into the water to excite the plating solution 18.
  • the ultrasonic generator is started before the cathode is submerged into the plating solution 18.
  • Plating current supply 24 applies a voltage between the anode 22 and cathode 20, preferably before the cathode is submerged into the plating solution 18. As the cathode 20 is submerged into the plating solution 18, the plating current starts to flow. It is desirable that the voltage from the plating current supply 24 and the ultrasonics be applied prior to the submersion of the cathode 20 into the plating bath 18 in order to avoid passivation of the cathode 20.
  • the alkaline gold double cyanide releases gold ions and changes to an alkaline cyanide.
  • the resulting alkaline cyanide residue such as potassium cyanide, remains in the plating solution 18 while the ultrasonics is on and falls to the bottom of the tank only after removal of the ultrasonics and cooling of the solution.
  • gold ion carrier potassium gold cyanide has been mentioned as a typical carrier of the gold, that other gold salts, such as other alkaline gold cyanides, which are compatible with the remaining components in the plating solution 18 may be used as the gold ion carrier.
  • EXAMPLE II In a second example, the potassium gold double cyanide and the potassium cyanide of Example I are used alone in an aqueous solution.
  • EXAMPLE III In a third example, between 7 and 9 troy ounces of gold (in the form of potassium gold double cyanide) per gallon of plating solution is used with from 3.6 ounces to 6 ounces of free cyanide per gallon of plating solution in the form of potassium cyanide and up to 2 ounces of sodium cyanide per gallon of plating solution.
  • the plating solution may also contain carbonates and Rochelle salts if desired.
  • a Wetting agent such as up to 0.1% by Weight of pentadecafluoro-octanoic acid or sodium laural sulfonate may be used.
  • the pH of the bath is maintained between 8 and 14 with a preferred range between 10.5 and 11.5 for brightness and smoothness.
  • FIGURE 2 a sketch of a metallographic section, magnified 1500 times, of a typical gold plate which is plated with a conventional acid bath, and no ultrasonic field, is shown. It is to be noted that it is completely non-crystalline in structure.
  • FIGURE 3 a sketch of a metallographic section, magnified 1500 times, of a gold plate which was plated in accordance with this invention at a current density of 30 amperes per square foot is shown. Note the columnar grains substantially perpendicular to the basis metal and the dense packing of the associated grain boundaries.
  • the gold is more densely packed, its electrical and thermal conductivity is increased. Because the produced hard surface is pure gold, it is joined more easily to other metals, by soldering and welding, than a gold alloy.
  • Electroforrning of gold may be achieved by any of the known processes in conjunction with the novel plating process and electrolyte of this invention. Examples of electroformed gold:
  • Example A Plate gold onto clean unactivated copper or aluminum, then physically withdraw the aluminum or copper.
  • Example B Deposit copper over plaster of appropriate shape, plate gold onto the copper, dissolve out the plaster with water and the copper with acid.
  • Example C Plate gold onto a basis metal, then machine oil the gold where it is not desired.
  • Copper, nickel, silver, and other conventional strike coatings may be used as a basis metal for the gold plate of this invention.
  • zincated aluminum may be covered with a copper strike before the gold is plated.
  • said electrolyte contains at least 5 troy ounces of gold in the form of alkali metal gold cyanide per gallon of electrolyte, said electrolyte is ultrasonically agitated, and said potential is sufiicient to plate with plating current densities in excess of that required to overcome the cavitation action of the ultrasonic agitation.
  • said gold is in the form of potassium .gold double cyanide and said plating bath further contains potassium cyanide in sufiicient quantity to adjust the pH of said bath to between 10.5 and 11.5.

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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)
US473746A 1965-07-21 1965-07-21 Method of electroplating and electroforming gold in an ultrasonic field Expired - Lifetime US3427231A (en)

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DE (1) DE1496889B2 (lm)
GB (1) GB1135099A (lm)
NL (1) NL6610168A (lm)
SE (1) SE306862B (lm)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3652442A (en) * 1967-12-26 1972-03-28 Ibm Electroplating cell including means to agitate the electrolyte in laminar flow
US3879269A (en) * 1973-04-26 1975-04-22 Auric Corp Methods for high current density gold electroplating
US4464231A (en) * 1980-10-22 1984-08-07 Dover Findings Inc. Process for fabricating miniature hollow gold spheres
US4830758A (en) * 1986-12-03 1989-05-16 Bodine Albert G Sonic method and apparatus for winning minerals from liquid carriers
US5207427A (en) * 1991-05-09 1993-05-04 Sumitomo Rubber Industries, Ltd. Golf club head and manufacturing method thereof
US5695621A (en) * 1996-07-31 1997-12-09 Framatome Technologies, Inc. Resonating electroplating anode and process
US6372116B1 (en) * 1998-11-14 2002-04-16 Hyundai Microelectronics Co., Ltd Method of forming a conductive layer and an electroplating apparatus thereof
US20160145756A1 (en) * 2014-11-21 2016-05-26 Rohm And Haas Electronic Materials Llc Environmentally friendly gold electroplating compositions and methods

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2090049A (en) * 1935-10-17 1937-08-17 Du Pont Cadmium plating
US2367314A (en) * 1941-06-24 1945-01-16 Western Electric Co Electrolytic method of coating localized areas of articles
US2801960A (en) * 1956-09-06 1957-08-06 Seegmiller Robert Gold plating process
USRE24582E (en) * 1958-12-23 Method and electrolyte for
US2967135A (en) * 1960-06-08 1961-01-03 Barnet D Ostrow Electroplating baths for hard bright gold deposits
US3020217A (en) * 1956-10-19 1962-02-06 Sel Rex Precious Metals Inc Mirror bright gold alloy electroplating
US3092559A (en) * 1961-05-01 1963-06-04 Sel Rex Corp Gold plating
US3112174A (en) * 1961-09-19 1963-11-26 Trifari Krussman And Fishel In Process for producing gold cyanide solutions of high gold content
US3149058A (en) * 1959-12-31 1964-09-15 Technic Bright gold plating process

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE24582E (en) * 1958-12-23 Method and electrolyte for
US2090049A (en) * 1935-10-17 1937-08-17 Du Pont Cadmium plating
US2367314A (en) * 1941-06-24 1945-01-16 Western Electric Co Electrolytic method of coating localized areas of articles
US2801960A (en) * 1956-09-06 1957-08-06 Seegmiller Robert Gold plating process
US3020217A (en) * 1956-10-19 1962-02-06 Sel Rex Precious Metals Inc Mirror bright gold alloy electroplating
US3149058A (en) * 1959-12-31 1964-09-15 Technic Bright gold plating process
US2967135A (en) * 1960-06-08 1961-01-03 Barnet D Ostrow Electroplating baths for hard bright gold deposits
US3092559A (en) * 1961-05-01 1963-06-04 Sel Rex Corp Gold plating
US3112174A (en) * 1961-09-19 1963-11-26 Trifari Krussman And Fishel In Process for producing gold cyanide solutions of high gold content

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3652442A (en) * 1967-12-26 1972-03-28 Ibm Electroplating cell including means to agitate the electrolyte in laminar flow
US3879269A (en) * 1973-04-26 1975-04-22 Auric Corp Methods for high current density gold electroplating
US4464231A (en) * 1980-10-22 1984-08-07 Dover Findings Inc. Process for fabricating miniature hollow gold spheres
US4830758A (en) * 1986-12-03 1989-05-16 Bodine Albert G Sonic method and apparatus for winning minerals from liquid carriers
US5207427A (en) * 1991-05-09 1993-05-04 Sumitomo Rubber Industries, Ltd. Golf club head and manufacturing method thereof
US5695621A (en) * 1996-07-31 1997-12-09 Framatome Technologies, Inc. Resonating electroplating anode and process
US6372116B1 (en) * 1998-11-14 2002-04-16 Hyundai Microelectronics Co., Ltd Method of forming a conductive layer and an electroplating apparatus thereof
US6797135B2 (en) 1998-11-14 2004-09-28 Hyundai Microelectronics Co., Ltd. Electroplating apparatus
US20160145756A1 (en) * 2014-11-21 2016-05-26 Rohm And Haas Electronic Materials Llc Environmentally friendly gold electroplating compositions and methods
KR20160061268A (ko) * 2014-11-21 2016-05-31 롬 앤드 하스 일렉트로닉 머트어리얼즈 엘엘씨 환경 친화적인 금 전기도금 조성물 및 방법
CN105624745A (zh) * 2014-11-21 2016-06-01 罗门哈斯电子材料有限责任公司 环保的金电镀组合物及方法
CN105624745B (zh) * 2014-11-21 2018-11-06 罗门哈斯电子材料有限责任公司 环保的金电镀组合物及方法

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DE1496889A1 (de) 1969-08-14
GB1135099A (en) 1968-11-27
SE306862B (lm) 1968-12-09
DE1496889B2 (de) 1971-10-21
NL6610168A (lm) 1967-01-23

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