WO1987005339A1 - Solution d'electrolyte et procede de dorure electrolytique a haute vitesse - Google Patents

Solution d'electrolyte et procede de dorure electrolytique a haute vitesse Download PDF

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Publication number
WO1987005339A1
WO1987005339A1 PCT/US1987/000513 US8700513W WO8705339A1 WO 1987005339 A1 WO1987005339 A1 WO 1987005339A1 US 8700513 W US8700513 W US 8700513W WO 8705339 A1 WO8705339 A1 WO 8705339A1
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WIPO (PCT)
Prior art keywords
liter
bath
gold
formic acid
set forth
Prior art date
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Ceased
Application number
PCT/US1987/000513
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English (en)
Inventor
Jean A. Lochet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Vanguard Research Associates Inc
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Vanguard Research Associates Inc
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Filing date
Publication date
Application filed by Vanguard Research Associates Inc filed Critical Vanguard Research Associates Inc
Publication of WO1987005339A1 publication Critical patent/WO1987005339A1/fr
Anticipated expiration legal-status Critical
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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
    • 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
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/62—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of gold

Definitions

  • This invention relates to the electrodeposition of gold from an aqueous soluble gold cyanide plating bath. More particularly, it relates to obtaining bright gold deposits at high temperatures and high plating rates, e.g. without degra- dation of the quality of the deposit.
  • an electrolytic bath for plating gold or a gold alloy which contains a cyanide of gold, a base metal salt such as of cobalt, nickel, indium, etc. , and citric acid plus sodium citrate or acetic acid plus sodium acetate.
  • a cyanide of gold e.g., a base metal salt such as of cobalt, nickel, indium, etc.
  • citric acid plus sodium citrate or acetic acid plus sodium acetate e.g. citric acid and its salt is clearly intended to act as a buffer to maintain the bath within a pH range of about 3-5.
  • the use of other weak acids such as lactic, formic, etc., is mentioned, but there is no demonstration of a bath containing formic acid.
  • U.S. Patent 3,104,212 differs from the above in that the base metal salt is omitted.
  • U.S. Patent 3,672,969 discloses a gold plating bath which contains an organophosphorus chelating compound, typically a phosphorus acid, e.g. amino-tri (methylphosphonic acid) or l-hydroxyethylidene-l,l-diphosphonic acid. As an improvement, a water soluble citrate is included in the bath. However, there is no mention of formic acid.
  • a complexing agent such as ethylenediaminetetraacetic acid (EDTA) is employed in the bath and a weak acid and salt thereof to provide a pH of 4.5 to 6.0, exemplified by KH2PO4 (a partially neutralized acid salt), partially neutralized citric acid, tartaric acid or acetic acid.
  • EDTA ethylenediaminetetraacetic acid
  • Patent 4,253,920 discloses a gold plating bath which includes potassium dihydrogen phosphate, a Cu or Ni hardefter/brightener and, as chelating agent, 1-hydroxyethyli- dene-1, 1-diphosphonic acid. No weak organic acids are present.
  • the chelating agent is nitrilotris (methylene) triphosphonic acid (sold as Dequest 2000).
  • 4,396,471 states that virtually any conductive acid or salt may be used as electrolyte and the composition of the electrolyte is not critical, mentioning weak organic acids such as malic, formic, and especially citric. Potassium citrate plus citric acid to buffer the bath, is recommended.
  • parts to be plated can be plated on a continuous ' basis on reel-to-reel selective plating machines, see "Continuous Reel-to-Reel Plating for' the Electronics Industry” by Jean ochet et al, an AES Electronics Lecture.
  • Such machines are very expensive and perform all the plating steps on a con ⁇ tinuous basis, including cleaning, activation, undercoating, and final plating of the parts by processing the parts, in successive steps, through the complete plating cycle.
  • their pro ⁇ cessing speed is only limited by the deposition speed, i.e. the ability of the plating baths to produce acceptable deposits of required thicknesses rapidly.
  • Formulations were proposed making use of so-called cur ⁇ rent extenders.
  • Such current extenders increase the bath's ability to plate at high current densities without the deposit being burnt.
  • a burnt deposit is spongy and black.
  • higher current densities mean higher rates of deposition, since theoretically one ampere will deposit a definite amount of metal in one second.
  • the current extender is a heterocylic azohydrocarbon sulfonic acid or salt thereof.
  • glycolic acid with a salt thereof is used as current extender.
  • High current density plating in the order of 500 to 1000 ASF at the cathode results in similar, and in some cases because of very small anode areas, in even higher anodic current densities.
  • Such high anodic current densities are highly unde ⁇ sirable because of anodic oxidation phenomena.
  • the cobalt and/or nickel brighteners/ hardeners usually present in the valency of 2 are oxidized to the higher valency of 3 and/or even changed to the highly undesirable inactive potassium cobalticyanide K ⁇ CCo CNjg] or similar hydroxy complexes of the same family.
  • the gold is also, in some cases, partially or even fully oxidized to the higher valency of 3, hence considerably reducing the efficiency and the rate of plat- ing.
  • oxygen is often absorbed by the electrolyte and decreases efficiency and worsens metal distribution, as discussed in U.S. Patent 3,669,852 recommending several methods to remove oxygen from gold plating baths.
  • U.S. patent 3,904,493 discloses gold sulfite plating baths containing organophosphorus compounds such as phosphonic acids.
  • a brightening agent such as nickel may be included in the baths.
  • a soluble gold cyanide e.g. an alkali metal gold cyanide
  • an organophosphorus chelating agent in particular a phosphonic acid
  • the preferred phosphonic acids are 1-hydroxyethyli- dene-1, 1-diphosphonic acid, sold under the tradename of Dequest 2010 and aminotri(methylene phosphonic acid) sold under the trade name Dequest 2000, both available from the Monsanto Company.
  • the formic acid acts as a current extender, permitting high current densities and also high temperatures to be used thereby achieving high plating speeds.
  • the amounts of formic acid are given in milli- liters.
  • the formic acid should be present in an amount of at least 20 ml/liter to about 150 ml/liter, preferably above 40 ml/ liter to about 90 ml /liter, more preferably above 40 ml/liter to about 50 ml/liter, based on the standard purified or C.P. grade containing approximately 90 weight % of formic acid. Concentra- tion of the organophosphorus compound in the range of 50-150 ml/1 have given good results.
  • the electrolyte or conductivity salt may, in some cases, be a mixture of an alkali metal monophosphate and a phosphonic acid or mixed phosphonic acids.
  • Cobalt or nickel which may be introduced as their salts or chelates, e.g. as the sulfate, may be used as brightener/ hardeners.
  • the cobalt or nickel concentration may be in the range of 350 to 600 mg/liter, preferably about 500 mg/liter.
  • the pH is also critical and it has been found that when cobalt is present the pH should be in the range of 4.0 to 4.2, and that when nickel is present the pH should be in the range of 3.8 to 3.9.
  • the gold concentration may range up to 30g/liter, pre ⁇ ferably may be in the range of 8 to 20 g/liter, e.g. 10 to 20 g/liter, but for some plating techniques may be lower, e.g. from 2 to 4 g/liter.
  • the addi ⁇ tion of formic acid and a chelating organophosphorus compound to the bath gives unexpected results, i.e., produces bright gold deposits at high deposition speed.
  • the plating may be accomplished by any of the commer- cial means available such as barrel, rack and strip plating equipment and high speed continuos selective plating equipment.
  • the products are useful for industrial purposes, especially for making electrical connections, e.g. as connectors.
  • plating may be carried out at tem- peratures in the range of 90 ⁇ to 160*F. and at current densitites from about 0.5 to an excess of 1000 ASF.
  • the process yields deposits having a cobalt or nickel content of .15 to .2% and a hardness in the range of 130-200 Knoop.
  • BRIEF DESCRIPTION OF THE DRAWINGS The Figure is a graph showing the effect of gold con ⁇ centration on plating speed at 100 ⁇ F. DETAILED DESCRIPTION
  • the invention will be described with reference to the ensuing tests and Examples, which are intended to be illustrated but not limitative. Extensive testing was carried out in order to provide a stable solution capable of plating at a higher rate and higher current densities than the currently commercially available solutions, without the problems discussed above.
  • PGC is an abbreviation for 68% potassium gold cyanide.
  • the cobalt may be any suitable soluble compound such as the sulfate or the complex of a suitable, compatible chelating compound or that of the organophosphorus compounds used in the formula.
  • the testing method used basically employs a 1 liter beaker with platinum coated anodes, a thermostatically controlled heater, a means to provide mild agitation and a suitable recti ⁇ fier in which are plated copper wires of about 1mm in diameter and 320mm in length turned around a wood cylinder of 2mm in dia ⁇ meter. These have the advantage over panels of giving a better idea of the bath overall plating abilities. All the wires plated in all the tests have a minimum gold thickness of 50 to 100 microinches. Test 1
  • EXAMPLE I The same formulation was used in a high agitation cell like the one described in U.S. Patent 4,431,500, with a gold con ⁇ centration of 15g/l. An excellent, about 54 microinch thick, bright gold deposit was obtained at a current density of 980 ASF, a temperature of 150"F., and a line speed of 25 feet/ minute. The retention time was 3.5 seconds and the efficiency was 39.3 mg per amp. min. , which gives a plating speed of 15.48 microinches per second of retention time. It should be noted that a high agitation cell like the one described in U.S. Patent 4,431,500 allows current densitites that are much higher, i.e. 6 to 10 -10-
  • the tempera ⁇ ture may suitably be in the range of 100° to 150 ⁇ F.
  • Such a bath is capable of producing a bright gold deposit at higher current densities, higher temperatures and higher plating rates than that of the prior art.
  • Cobalt-metal (as complex) 500 milligrams
  • TEST 7 Plating temperature 150 ⁇ F.
  • the object of the test was to find out the limits of the bath at high current densities. Thus, the current density was increased until burning of the deposit took place.
  • a bath was prepared similar to that used in Test 1, but without excess Dequest 2010, as shown in Formula D below, and was used in Test 9.
  • Au-metal (as PGC) 10 grams The thin copper wires of the type used in Test 1 were plated in the above solution and the results are set forth below. The plating temperature was 150"*F.
  • Test 11 5 ml of formic acid: Current Density 80 ASF 120 ASF 150 ASF Efficiency 45.0 mg 30.0 mg 27.0 mg
  • Test 13 (20 ml of formic acid): Current Density 40 ASF 80 ASF 120 ASF 150 ASF Efficiency 54 mg 45.0 mg 37.0 mg 30.0 mg Appearance semi- semi- semi- bright bright bright dull Test 14 (30 ml of formic acid) : Current Density 40 ASF 80 ASF 120 ASF 150 ASF Efficiency 56.5 mg 45.0 mg 34.0 mg 30.0 mg Appearance semi- semi- semi- bright bright dull dull
  • Test 16 (Formic acid 75 ml) : Current Density 40 ASF 80 ASF 120 ASF 150 ASF Efficiency 54 mg 43 mg 37 mg 30 mg
  • Nickel may be substituted for cobalt in similar formu ⁇ lations, however, the preferred pH for more consistent color is 3.8 to 3.9 instead of 4.0 to 4.1 for cobalt.
  • the nickel content of the deposits was found to be in the range of .2 to .3% depending on the conditions of deposition. Tests have also shown that the addition of alkali phos- phates, with the exception of ammonium phosphate, is not desir ⁇ able, as they have a tendency to render the bath unstable result ⁇ ing in precipitation of the gold and the nickel in the form of one or more unknown compounds. Furthermore, Dequest 2000 is preferred over Dequest 2010 and Dequest 2041 in the above formula- tion for nickel. -19-
  • the bath of Test 1 was modified in order to optimize distribution of the gold deposit.
  • the cobalt content is suitably kept in range of 350 to 415/mg/liter, prefer ⁇ ably at about 380 rag/liter.
  • the following formulation, desig ⁇ nated Formula H, was used in Example II with the gold concentra ⁇ tion at 4 g/liter.
  • a plating temperature in the range of 90* to 110 ⁇ F. was selected mainly because it gave a color identical to that of the high speed formulation of Test 1. Higher temperatures may be used.
  • Optimum gold concentration depends on the application and should be adjusted accordingly.
  • the graph of the figure shows the effect of gold concentrations on efficiency and plating speed. Plating rate in miocroinches per minute is ' plated against current density for gold concentrations respectively of 4 grams per liter and 6 grams per liter, at 100 ⁇ F. It will be seen that higher gold concentration increases plating rate.

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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)

Abstract

Dépôt électrolytique d'or par électrolyse d'une solution aqueuse contenant du cyanure d'or de potassium, comprenant une concentration critique d'acide formique, d'un agent de chélation du type acide phosphonique et d'un composé de cobalt ou de nickel, à un pH critique, pour obtenir des vitesses de placage extrêmement élevées. On peut utiliser des températures de placage relativement élevées, dans la gamme comprise entre 90° et 160°F et des intensités de courant élevées allant jusqu'à 1000 ASF, de manière à atteindre des vitesses de placage élevées sans dégradation de la qualité du dépôt.
PCT/US1987/000513 1986-03-05 1987-03-02 Solution d'electrolyte et procede de dorure electrolytique a haute vitesse Ceased WO1987005339A1 (fr)

Applications Claiming Priority (2)

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US83624086A 1986-03-05 1986-03-05
US836,240 1986-03-05

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114892225A (zh) * 2021-09-30 2022-08-12 深圳市联合蓝海黄金材料科技股份有限公司 用于在镍镀层上电镀金的镀液和在镍镀层上电镀金的方法和镀金件与应用

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1909144A1 (de) * 1969-02-20 1970-09-17 Schering Ag Elektrolyt zum Abscheiden glaenzender Goldlegierungsniederschlaege
US4073700A (en) * 1975-03-10 1978-02-14 Weisberg Alfred M Process for producing by electrodeposition bright deposits of gold and its alloys
GB2093069A (en) * 1981-02-17 1982-08-25 Hooker Chemicals Plastics Corp Gold electroplating bath and process

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1909144A1 (de) * 1969-02-20 1970-09-17 Schering Ag Elektrolyt zum Abscheiden glaenzender Goldlegierungsniederschlaege
US4073700A (en) * 1975-03-10 1978-02-14 Weisberg Alfred M Process for producing by electrodeposition bright deposits of gold and its alloys
GB2093069A (en) * 1981-02-17 1982-08-25 Hooker Chemicals Plastics Corp Gold electroplating bath and process

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114892225A (zh) * 2021-09-30 2022-08-12 深圳市联合蓝海黄金材料科技股份有限公司 用于在镍镀层上电镀金的镀液和在镍镀层上电镀金的方法和镀金件与应用
CN114892225B (zh) * 2021-09-30 2023-03-14 深圳市联合蓝海黄金材料科技股份有限公司 用于在镍镀层上电镀金的镀液和在镍镀层上电镀金的方法和镀金件与应用

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EP0261203A1 (fr) 1988-03-30

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