EP0458828A1 - Beschichtungszusammenstellung und -verfahren - Google Patents

Beschichtungszusammenstellung und -verfahren

Info

Publication number
EP0458828A1
EP0458828A1 EP19900903038 EP90903038A EP0458828A1 EP 0458828 A1 EP0458828 A1 EP 0458828A1 EP 19900903038 EP19900903038 EP 19900903038 EP 90903038 A EP90903038 A EP 90903038A EP 0458828 A1 EP0458828 A1 EP 0458828A1
Authority
EP
European Patent Office
Prior art keywords
composition
cobalt
plating
ions
cadmium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19900903038
Other languages
English (en)
French (fr)
Inventor
Ian Gerald Mcdonald
Philip John Archer
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.)
POLYMETALS TECHNOLOGY Ltd
Original Assignee
POLYMETALS TECHNOLOGY Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB898903646A external-priority patent/GB8903646D0/en
Priority claimed from GB898903645A external-priority patent/GB8903645D0/en
Application filed by POLYMETALS TECHNOLOGY Ltd filed Critical POLYMETALS TECHNOLOGY Ltd
Publication of EP0458828A1 publication Critical patent/EP0458828A1/de
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
    • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents

Definitions

  • This invention relates to electroless cobalt plating.
  • Electroless deposition in general is a known technique. It is a process whereby metal ions in solution are reduced to metal atoms on a surface which is to be plated. Electroless plating is distinguished from electroplating, in which the reducing power is supplied by electricity, by the provision of a chemical reducing agent.
  • Electroless- cobalt deposition is itself known. Pearlstein and Weightman (J. Electrochem. Soc. (1974) 1023-1028) have described the electroless deposition of cobalt from acid baths. They reported that the coercivity of certain electroless cobalt-boron deposits was low, and electroless cobalt has been used in the preparation of magnetic memory surfaces.
  • cobalt does have certain advantages: for example, electroless cobalt depositions have been able to withstand higher temperatures than corresponding nickel depositions, which is advantageous in some applications.
  • the bath is thermodynamically unstable.
  • the metal ions which are to be deposited are usually complexed so as to prevent their reduction to metal in the bulk of the solution; but the metal ions should not be so strongly complexed that the deposition of the metal onto the substrate to be plated will be prevented.
  • the surface of the substrate will usually be to some degree catalytic (either inherently or by being rendered catalytic) for the reduction of the metal ion to the metal.
  • Thallium has previously been reported as a stabiliser for certain electroless nickel deposition systems. Unfortunately, thallium does not seem to be particularly effective for cobalt, and in any case it is extremely toxic. There is therefore a need for a means of stabilising baths for producing electroless cobalt deposits.
  • cadmium can act as a stabiliser for such baths. It also appears that cadmium can act as a brightener and increases bath life. Cadmium can also act as a grain refiner.
  • an electroless cobalt plating composition comprising a source of cobalt ions, a reducing agent and cadmium ions in an amount effective to stabilise the composition but insufficient substantially to prevent cobalt deposition on a substrate.
  • any convenient' and sufficiently soluble salt of cobalt may be used.
  • Cobalt sulphate or cobalt chloride is generally found to be convenient.
  • the source of cobalt may be present in an amount of from 1 to 100 g/1, for example 10 to 45 g/1, typically about 30 g/1, calculated as cobalt sulphate hexahydrate.
  • the cobalt deposit may contain a minor amount, for example up to 15, 20, 25 or 30%, of an alloying metal such as nickel.
  • the amount of cobalt in the plating composition may be (but is not necessarily) slightly less than the middle of the broad and preferred ranges given above.
  • a source of alloying metal such as nickel may be present to provide metal ions in an amount of from 0.1 to 3 g/1, preferably 0.5 to 1.5 g/1; these amounts could be realised by providing, for example, 0.45 to 13.5 g/1, and preferably 2.25 to 6.75 g/1, nickel sulphate hexahydrate. ⁇
  • a complexor will u-sually be present to maintain the cobalt and/or alloying metal in solution under the appropriate operating conditions.
  • Any suitable complexor may be used, but carboxylic acids (for example C-_-Cg carboxylic acids) , particularly dicarboxylic acids (for example C 2 -C 10 carboxylic acids) may be advantageous.
  • Succirtic acid has been found to be the most appropriate, but other suitable acids include acetic, glycollic, oxalic, glutaric and adipic acids.
  • the complexor may be present in an amount of from 1 to 100 g/1, for 'example 5 to 4.0 g/1, typically about 25 g/1.
  • both the source of cobalt and the complexor may be provided as a single source, for example cobalt succinate.
  • cobalt succinate References in this specification to weak (eg organic) acids are to be taken to include their salts, and vice versa, as the exact nature of the species present will depend on the pH.
  • any appropriate reducing agent may be used. Hitherto, dimethylamino borane (DMAB) has been found to be the most appropriate. It appears that the use of such a reducing actually yields electroless deposits of cobalt-boron, much in the way as the use of hypophosphite in electroless nickel plating produces nickel-phosphorus. It is to be understood that in this specification the word "cobalt”, when referring to the deposited metal includes such entities as cobalt-boron alloys, cobalt phosphorus alloys and compositions of cobalt, boron and phosphorus.
  • DMAB dimethylamino borane
  • Boron hydrides and their derivatives in general and alkyl amino boranes are suitable reducing agents.
  • Mixtures of more than one reducing agent such as DMAB and hypophosphite can be used.
  • the reducing agent may be present in an amount of from 0.5 to 20 g/1, for example from 2 to 6 g/1, typically about 4 g/1.
  • the amount of cadmium that is to be present is to be chosen.so as to be sufficient to stabilise the bath, but insufficient substantially to prevent the cobalt being deposited on the substrate. Too high a concentration of cadmium is believed to poison the catalytic qualities of the substrate.
  • the amount of cadmium that is suitable for use in the invention may vary depending on the bath conditions, but will generally be in the order of less than 15 ppm, for example from 0.1 to 8 ppm, typically from 0.5 to 7 ppm, and preferably about 6 ppm. Appropriate amounts can be determined by simple experimentation within the general teaching of this specification.
  • the cadmium may be added in ionic form or covalently bound in a compound or as the free metal, in which case it will generally dissolve to form a salt. It is preferably supplied as a soluble salt, such as cadmium acetate. The amount of cadmium present is calculated by reference to the metal.
  • the plating composition can contain a further stabiliser and/or grain refiner.
  • An example is lead.
  • the use of lead in electroless cobalt plating baths is the subject of another application filed today confrontby the same applicants as are named in this application and claiming the same two priorities; where the law allows, the other application is herein incorporated by reference.
  • the amount of lead that is to be present may be chosen so as to be sufficient, in combination with other bath components, to refine the structure of the deposit produced and/or to stabilise the composition (particularly when depositing composites) , but insufficient substantially to prevent the cobalt being deposited on the substrate. Too high a concentration of lead is believed to poison the catalytic qualities of the substrate.
  • the amount of lead that is suitable for use in the invention may vary depending on the composition conditions, but will generally be in the order of from 0.5 to 40 ppm, for example about 1 to 20 ppm. Appropriate amounts can be determined by simple experimentation within the general teaching of this specification.
  • the lead may be provided simply by adding a source of lead ions to the composition (for example in an amount of from 1 to 10 ppm, typically 3 to 5 ppm) and/or it may be provided, in the case of composite plating compositions, by pre-treating additive particles (when present) with lead and adding the so-treated particles to the plating composition. Additive particles are discussed further below.
  • additive particles may be pre-treated with cadmium, tin, zinc, mercury, thallium, bismuth and/or antimony.
  • the plating composition may contain an accelerator.
  • Accelerators act to improve the plating rate.
  • Sulphur-containing compounds in general are good accelerators, although their use in excess can be marked by a deterioration in surface quality.
  • Some sulphur-containing compounds such as thiourea are initially effective but prone to hydrolysis.
  • Preferred accelerators are therefore sulphur-containing compounds which are generally stable to hydrolysis.
  • An example of such a compound is mercaptobenzothiazole (MBT) which may be used in an amount of from 0.1 to 20 ppm, for example 1 to 5 ppm and typically about 2 ppm.
  • the composition may contain a moderator. Lactic acid has been found to have an effect on the overall quality of the plating operation, for example by enhancing stability and improving the structure of the deposit. Lactic acid is known for use in nickel-hypophosphite electroless plating compositions, where it has the effect of removing an unwanted by-product. Here it is having a different effect.
  • the lactic acid may be present in the composition in an amount of from 0.1 to 30 ml/1, for example 1 to 10 ml/1, typically about 5 ml/1.
  • the composition may contain a wetting agent, for example to reduce surface tension as an aid to the release of gas bubbles.
  • a wetting agent for example to reduce surface tension as an aid to the release of gas bubbles.
  • surfactants are suitable, particularly nonionic and anionic surfactants.
  • Ethoxylated alkyl phenols exemplified by those sold under the trade mark TRITON XT 100, are a
  • suitable class of nonionic surfactants, and sulphosuccinates, such as those sold under the trade mark LUTENSIT ABP are a suitable class of anionic surfactants.
  • the wetting agent may be present in an amount of from 1 to 75 ppm for anionic surfactants or from 1 to 40 ppm for nonionic surfactants. Amounts in the range of from 1 to 5 ppm are typically used.
  • the composition may contain additive particles for forming a composite coating.
  • the additive particles may be of any suitable material.
  • Additive particles which may be used include graphite, polyfluorocarbons such as polytetrafluoroethylene (ptfe) , carbides, oxides, borides and nitrides; even non-catalytic metallic particles such as molybdenum can be co-deposited to provide another family of composites.
  • Silicon carbide is a particularly preferred additive particle because it is available in purified form and a wide range of particle sizes, is reasonable in cost and has been found to be excellent in performance.
  • Chromium carbide and chromium oxide particles are the additive particles of choice in the aeronautical industry. The particles may range from 0.5 to 50 microns in size, for example 1 to 5 microns and typically about 2 microns.
  • the additive particles may be present in the electroless deposition composition in an amount of from 0.1 to 50 g/1, typically 0.5 to 10 g/1, for example about 2 g/1.
  • the pH of the plating composition will generally be on the acid side, but if the pH is too low, the plating rate is reduced. It is therefore preferred for the bath pH to be in the range of from 4.5 to 6.5, for example about 4.8 to 5.5.
  • a process for the electroless deposition of cobalt onto a substrate comprising contacting the substrate with a composition comprising a source of cobalt ions, a reducing agent and cadmium ions in an amount effective to stabilise the composition but insufficient substantially to prevent cobalt deposition on the substrate.
  • the temperature of the composition in use may be adjusted as desired. A higher temperature results in a faster plating rate, but there are corresponding sacrifices in the energy consumption of the system. It is generally preferred for the temperature to be in the range of from 60 to 90°C, for example from 70 to 85°C.
  • the method of contacting the surface of the substrate to be plated with the composition will usually be immersion in a bath of the composition.
  • immersion is not necessarily the only suitable method. It may, for example, be possible to develop a suitable spray-plating method.
  • the time of contact between the substrate and the plating composition will naturally depend on the thickness of the deposit required and the plating rate. Contact times in the order of 5 minutes to 5 hours may be appropriate, with contact times of from 30 minutes to 2 hours being typical.
  • the plating rate itself will generally be optimised to a degree that is compatible with the quality required of the finished product.
  • Plating rates in the range of 20 to 30 microns per hour are generally achievable by means of the invention, but higher quality deposits may be achievable by more modest plating rates.
  • agitate the composition during plating In order to enhance the evenness of the deposit, it is usual to agitate the composition during plating. Agitation may be achieved by any suitable means such as mechanical stirring, pump agitation, magnetic stirring and air agitation.
  • the plating may take place on any suitable substrate. Steel and other metals are preferred substrates. It is not essential that any pre-treatment of the substrate take place, although for non-conductive substrates an activator such as palladium may be deposited. Cleaning and desmutting operations may be appropriate, as will be known to those skilled in the art. When working with steel, a thin electroless nickel deposit may be used with advantage as an undercoat. Any suitable electroless nickel plating composition may be used, such as that supplied by Lea Manufacturing Co Ltd of Buxton, England under the trade mark ALLIED KELITE 794. Plating may take place for as little as 5 minutes to produce a very thin substantially pure nickel layer.
  • a cobalt electroless plating bath (3 litres) of the following composition was prepared:
  • the bath was replenished by the addition of CoS0 4 (20 g) and DMAB (4 g) and plating continued for a further 90 minutes.
  • the replenishment and plating procedures were repeated a further four times, so that the coupon had been plated for a total of 9 hours: the bath was still stable.
  • New test coupons were then electrocleaned at 2 V for 10 minutes, after which they were subjected to two further 90 minute plating periods in the same bath as previously, with prior replenishment of cobalt and reducing- agent as before. Again, bath stability was maintained throughout.
  • Example 2 Example 2
  • a cobalt electroless plating bath of the following composition was prepared:
  • Example 2 The procedure of Example 2 was repeated except that the cadmium was present at 4 ppm. The weight gain was 0.3695 g and the plating rate was 22.17 microns/hour. The bath remained stable throughout.
  • Example 5 The pr.ocedure of Example 2 was repeated except that the cadmium was present at 6 ppm. The weight gain was 0.3543 g and the plating rate was 21.26 microns/hour. The bath remained stable throughout.
  • Example 5 The pr.ocedure of Example 2 was repeated except that the cadmium was present at 6 ppm. The weight gain was 0.3543 g and the plating rate was 21.26 microns/hour. The bath remained stable throughout. Example 5
  • Example 1 was repeated except that the bath contained 6g/l cobalt (as 26.7 g/1 CoS0 4 .6H 2 0) and lg/1 nickel (as 4.46 g/1 NiS0 4 .6H 2 0) .
  • This bath produces cobalt coatings containing approximately 10% by weight of nickel.
  • the presence of cadmium to the plating bath causes the surface of the deposit to appear laminar, when viewed under a metallurgical microscope (magnification 200X) . This contrasts with a nodular appearance observed if cadmium is not present.
  • Example 2 An electroless cobalt solution was prepared as in Example 1 but containing 6g/l cobalt (as cobalt sulphate hexahydrate) no added cadmium and 2ppm lead. Test coupons were plated with additions made of cobalt sulphate and dimethylamine borane only to maintain the bath chemistry. When 18g of cobalt metal had been deposited and the additions made, plating out occurred on the bottom of the beaker. The solution was filtered and reheated to operating temperature whereupon decomposition began to occur. Filtration was again carried out and the solution regenerated by the addition of cobalt sulphate and dimethylamine borane.
  • the lead in the bath was replenished by the addition of 6mg lead to give a working concentration of 2ppm.
  • the bath was reheated to 70°C and plating resumed. No sign of solution decomposition was evident until a further 18g metal had been deposited.
  • Example 6 The procedure of Example 6 was repeated, except that in order to refine the deposit structure, 2ppm cadmium (as cadmium acetate) was added to the plating bath. No deleterious affect on plating rate was noticed.
  • the deposit produced from this solution had a high degree of reflectivity. When viewed under the microscope (magnification 200X) , the surface structure appeared to be laminar as opposed to nodular when no cadmium is present in the solution.

Landscapes

  • 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)
EP19900903038 1989-02-17 1990-02-16 Beschichtungszusammenstellung und -verfahren Withdrawn EP0458828A1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB8903646 1989-02-17
GB898903646A GB8903646D0 (en) 1989-02-17 1989-02-17 Plating composition and process
GB8903645 1989-02-17
GB898903645A GB8903645D0 (en) 1989-02-17 1989-02-17 Plating composition and process

Publications (1)

Publication Number Publication Date
EP0458828A1 true EP0458828A1 (de) 1991-12-04

Family

ID=26294974

Family Applications (2)

Application Number Title Priority Date Filing Date
EP19900903038 Withdrawn EP0458828A1 (de) 1989-02-17 1990-02-16 Beschichtungszusammenstellung und -verfahren
EP19900903037 Withdrawn EP0458827A1 (de) 1989-02-17 1990-02-16 Beschichtungszusammenstellung und -verfahren

Family Applications After (1)

Application Number Title Priority Date Filing Date
EP19900903037 Withdrawn EP0458827A1 (de) 1989-02-17 1990-02-16 Beschichtungszusammenstellung und -verfahren

Country Status (3)

Country Link
EP (2) EP0458828A1 (de)
JP (2) JPH04503378A (de)
WO (2) WO1990009467A1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3142018B2 (ja) * 1992-03-12 2001-03-07 日本テキサス・インスツルメンツ株式会社 負荷駆動回路
JP2003049280A (ja) * 2001-06-01 2003-02-21 Ebara Corp 無電解めっき液及び半導体装置

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1209408A (fr) * 1957-11-04 1960-03-01 Du Pont Dépôt par voie chimique d'alliages de nickel-bore et de cobalt-bore
GB842826A (en) * 1957-11-15 1960-07-27 Du Pont Improvements in or relating to chemical plating
DE1621206B2 (de) * 1967-01-18 1971-12-16 Friedr. Blasberg Gmbh & Co, Kg, 5650 Solingen Verfahren zur beschichtung gleitend reibend auf verschleiss beanspruchter werkstuecke
US3562000A (en) * 1968-10-25 1971-02-09 Gen Am Transport Process of electrolessly depositing metal coatings having metallic particles dispersed therethrough
DE1950983A1 (de) * 1969-10-09 1971-04-22 Bayer Ag Waessriges,alkalisches Bad zur chemischen Metallisierung von Nichtleitermaterialien

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9009468A1 *

Also Published As

Publication number Publication date
JPH04503378A (ja) 1992-06-18
EP0458827A1 (de) 1991-12-04
WO1990009468A1 (en) 1990-08-23
JPH04503379A (ja) 1992-06-18
WO1990009467A1 (en) 1990-08-23

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