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
  • C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
  • C25D3/52—Electroplating: Baths therefor from solutions of platinum group metals characterised by the organic bath constituents used
• • 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
  • C25D3/567—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of platinum group metals

Definitions

• the present invention relates to an electrolytic bath intended for deposition electrochemical of palladium or its alloys as well as a process electroplating palladium or one of its alloys.
• the electrical contacts and connectors used in the field of electronics use, in finishing, thin layers of precious metals, electrodeposited which must be of suitable gloss, good ductility, non-porous, corrosion-resistant, friction-resistant and have low contact resistances.
• the industry began by using deposits, often referred to as "Hard Gold", of gold hardened with small amounts of nickel or codeposited cobalt. Palladium is a precious metal with a lower deposit density (12 g / cm 3 ) than "Hard Gold” deposits (17.3 g / cm 3 ), also with higher hardness and lower porosity. Cheaper, palladium and its alloys have been found suitable for replacing gold for most applications.
• the industry uses thin deposits (also referred to as flash-type deposits) of gold on palladium or on palladium alloys for finishing.
• the palladium alloys used are mainly palladium-nickel, or palladium-silver alloys.
• the barrel, the vibrating basket, the attachment, the discontinuous metallization, continuously high speed, or the jet deposition, also known by the term “jet-plating” deposition, or with the pad are commonly used techniques, for electrodepositing palladium and its alloys.
• the industry is constantly looking for electrolytic baths and more efficient processes. Palladium and its alloys are also used for decorative applications, as an undercoat or as a finish.
• the palladium and alloy baths currently sold are mostly ammonia baths, most often containing ions chlorides. These baths remain nevertheless baths with strong nuisances, so much for the health of operators, that for corrosion of equipment, they require many maintenance and upkeep operations.
• Ammonia tends to evaporate at room temperature, a lot of commercial baths and, in particular, so-called “high speed” baths, operate from 40 to 60 ° C. These baths generate strong gaseous fumes in the processing workshops; not only are these vapors irritating to the airways respiratory agents, but are corrosive to all copper metals surrounding, including for parts of parts not submerged in the electrolyte.
• the ammoniacal baths are conventionally alkaline baths, operating in pH ranges between 8 and 13.
• the alkalinity of the electrolyte promotes the passivation of nickel, which can cause a lack of adhesion of palladium alloy deposits.
• the first baths of this type described were baths of pure palladium, in very acidic environments, without organic amines. They were difficult to use, In fact, at pH values between 0 and 3, the attack on the substrates is too great. In addition, many of these formulations contain chlorides.
• a second type relates to baths of pure palladium or of alloy, which contain organic amines, operating from 40 to 65 ° C, but typically in a pH range from 9 to 12, therefore under strongly alkaline conditions. AT these high pH, at these temperatures, polyamines tend to evaporate strongly, and to carbonate quickly by generating crystallizations. On the other hand, in these conditions, the passivation of nickel-plated substrates is then even more important than in ammonia baths. To overcome the lack of grip, a pre-palladium is necessary as a preliminary. This increases the cost of these deposits.
• a third type of bath of pure palladium containing organic amines is described in particular in US Pat. No. 4,278,514.
• These baths of intermediate pH located from 3 to 7 generally contain phosphates, and use as a brightener an imide type compound, such as than succinimide.
• the admissible current densities are less than 4 A / dm 2 .
• these baths contain pure palladium and are therefore mainly intended for decoration.
• the imide-type compounds are capable of improving the brightness of these baths of pure palladium at low current densities, but the maximum current densities giving brilliant deposits do not exceed 4 A / dm 2 . Furthermore, to obtain this brightening action, the imides are added in large quantities. However, imides are strong complexing agents and their concentration therefore has a strong influence on the complexing of any incorporated secondary metal. This makes it too difficult to control the composition of the alloys, under suitable gloss conditions.
• the present invention precisely proposes an optimal formulation, to meet all these requirements.
• a problem which arises particularly for electronic applications is that of finding an effective brightener with very high current density, in a non-ammoniacal medium. Indeed, as explained above, many brighteners, and this is in particular the case of imide type brighteners, only allow glossy deposits to be obtained at medium or low current densities. In non-ammoniacal baths, known commercial brighteners such as nicotinamide, or sulfonate-type compounds, are not able to extend the gloss of deposits at high current densities, in particular those between 15 and 150 A / dm 2 desired in so-called "high speed" plating baths.
• US Patent 4,767,507 describes gold plating baths using uses two specific brighteners, namely 3- (3-pyridyl) acrylic acid or 3- (3-quinolyl) acrylic acid.
• these brighteners can also be used in electrolyte baths intended for the electrochemical deposition of palladium or its alloys in the presence of ethylenediamine acting as an agent complexing palladium.
• these brighteners are particularly active for the high densities of current, even in very low concentrations.
• the invention made it possible to find conditions where, in the absence chlorides and ammonia, plating could be done without deposit of insoluble salts on the anodes, which makes it possible to envisage applications in "jet-plating" and in continuous selective metallization of the metallization type at buffer.
• the invention relates to an aqueous electrolytic bath at acid pH for deposition electrochemical of palladium or its alloys comprising a compound of palladium, and optionally at least one compound of a secondary metal intended to be codeposited in the form of an alloy with palladium, and comprising in addition, ethylenediamine as a complexing agent for palladium and an agent organic brightener, characterized in that said brightening agent is 3- (3-pyridyl) acid acrylic, 3- (3-quinolyl) acrylic acid or a salt thereof, preferably one of their alkaline salts, for example a sodium or potassium.
• the bath of the invention makes it possible to deposit palladium or alloys of palladium, in particular alloys containing from 60 to 100% of palladium and 40 to 0% of one or more secondary metals such as: nickel, cobalt, iron, indium, gold, silver, or tin.
• the baths according to the present invention are completely ammonia-free, both in their constitution and in their maintenance.
• ethylenediamine as complexing agent which, at acidic pH, is very not very volatile, there is no emission of irritating vapors for the tracks operators' respiratory systems. Can operate at 75 ° C, without actually smell noticeable, these baths therefore allow operating temperatures above those practiced with ammonia baths (40 to 60 ° C), which is interesting for high speed electronic filing.
• the electrolytic baths of the invention are baths with a low pH acid, preferably at a pH between 3 and 5. Indeed, in this range of pH, the baths of the invention prove to be particularly stable. This pH range is particularly suitable for baths containing nickel or cobalt, the hydroxides may precipitate at pH between 6 and 7 and allow to avoid obtaining veiled deposits, as is the case for certain pH baths between 5 and 6.
• the gloss of the deposits obtained is generally further increased by the presence of a secondary metal which plays the role of mineral shine and, in a way analogous to what is observed in acidic gold baths.
• the electrolytic bath will advantageously contain between 0 and 60 g / l at least one metal acting as a mineral shine.
• One of the features of the baths according to the present invention is that they operate at weakly acidic pH preferably between 3 and 5.
• the baths of the invention are intended for deposition of palladium or its alloys, in particular alloys containing minus a secondary metal such as nickel, cobalt, iron, indium, gold, silver or tin in proportions of 0.1 to 40%.
• the baths of the invention advantageously contain from 1 to 100 g / l of palladium.
• they contain at least one metal secondary selected from the group consisting of nickel, cobalt, iron, indium, gold, silver and tin, at a concentration between 0.1 and 60g / l.
• one of the essential constituents of the the invention is ethylenediamine which acts to complex and therefore dissolve the palladium in the bath.
• This ethylenediamine is contained in the bath in sufficient amount to complex the palladium and make it soluble in said bath, preferably at a concentration between 2 and 200 ml / l.
• the specific brightening agent used according to the invention namely the acid 3- (3-pyridyl) acrylic or 3- (3-quinolyl) acrylic acid or a salt thereof, is contained in the bath at concentrations advantageously between 0.01 and 3 g / l.
• these two brighteners can be used at relatively low concentrations and with high current densities, in particular with current densities of up to 150 A / dm 2 , which makes it possible to envisage the application of the baths of the invention in particular as a high-speed bath for producing shiny deposits. They can also be used for jet plating and selective metallization applications.
• the electrolytic baths of the invention can contain various additives conventionally used in electroplating baths such only conductive salts, buffers to stabilize the pH, agents wetting agents, additives intended to reduce the internal stresses of deposits Electrolytic.
• the baths of the invention advantageously contain at least 20 g / l at least one conductive salt.
• This conductive salt will advantageously be chosen from the group consisting of sodium sulfate, potassium sulfate and their mixtures.
• the buffers intended to stabilize the pH will preferably be of the type acetic, citric, boric, lactic, malic, phthalic, acrylic, tartaric, oxalic or succinic.
• wetting agents are used.
• the agents preferred wetting agents according to the invention will be bromide or iodide of cetyltrimethylammonium.
• the invention proposes conditions allowing in particular to totally avoid the use of chlorides.
• the baths according to the present invention are advantageously without chlorides and the basic anion of these baths is advantageously sulphate.
• He is in known effect that sulfate anions are often used in electroplating because they react much less easily to electrodes, than nitrites or sulfites, the concentrations of which are much more difficult to maintain at a stable level in the electrolyte. These composition fluctuations can lead to to veiled deposits.
• the baths of the invention have very good stability.
• the palladium in the form of a compound specifically adapted for this purpose is the subject of a request for patent filed on the same day as this application.
• this compound which is in the form of a salt insoluble in water present the advantage of being able to be transformed in the presence of an excess of ethylenediamine into a soluble complex upon its introduction into the bath.
• this compound makes it possible to introduce palladium with a significantly lower amount of counterions (sulfate) than in the prior art.
• palladium was introduced into the electrolytic baths either in the form of one of its salts, for example its sulfate, or, where appropriate, directly as the water-soluble complex between the sulfate and ethylenediamine.
• palladium is introduced into the electrolytic bath of the invention in a particularly advantageous form in the form of a solid salt of palladium sulfate and of ethylenediamine comprising from 31 to 41% by weight of palladium and in which the molar ratio [SO 4 ]: [Pd] is between 0.9 and 1.15 and the [ethylenediamine]: [Pd] ratio is between 0.8 and 1.2.
• Secondary metals can also be introduced in the form of sulfate.
• the secondary metals will advantageously introduced in the form of sulfates, carbonates, hydroxides or their mixtures.
• the invention make it possible to extend the life of electroplating equipment by avoiding their corrosion.
• the invention also relates to a process for the electrodeposition of palladium or a palladium alloy, characterized in that it comprises the electrolysis of an electrolytic bath as defined above by implementing current densities between 0.5 and 150 A / dm 2 .
• the process of the invention is particularly advantageous. in electronic applications, where we try to work with a speed of maximum deposit and where the desired deposits should be, among other things, brilliant, ductile, non-porous. To obtain high productivity, the baths must operate under the highest possible current density and temperature and high agitation is often necessary. Ethylene diamine baths allow operating temperatures higher than that practiced with baths ammonia exposed to the generated gaseous fumes.
• the specific gloss of the invention can be used in baths of palladium and palladium alloys, where it's also very effective, like bright at high current densities and even at very low concentrations.
• the baths of the invention therefore admit current densities similar to, or greater than, the most efficient ammonia baths.
• bright deposits of 0.1 to 6 ⁇ m can be produced at current densities between 0.5 to 150 A / dm 2 .
• baths of the invention can also be used for lower speeds and densities of current and, in particular, in decoration applications.
• the anodes are insoluble anodes, preferably platinum titanium, oxide coated platinum iridium or a precious metal such as platinum. Furthermore, the cathode is made of a metallized substrate.
• the concentrations of palladium and alloy metals are related to metal.
• This method of adding palladium to the electrolyte can be used for the first preparation of the bath, and for palladium readjustments during of operation.
• This bath deposits the 80% palladium - 20% nickel alloy.
• the deposit of 0.1 to 6 ⁇ m is mirror-gloss, ductile, with low contact resistance, hardness Vickers of 390 HV under 100 gf (measured according to ISO standard 4,516 (1980)).
• the deposits checked according to iso 4524/3 (85), are non-porous, they have a good corrosion resistance and, for a thickness of 0.5 to 6 ⁇ m, they are conforms to the so-called "CASS TEST" test defined by standard ISO 9 227 (1990). Through elsewhere, they have good resistance to friction and pass the test positively says "BRITISH TELECOM".
• This bath deposits the palladium alloy 75% - cobalt 25%, the deposit from 0.1 to 6 ⁇ m is mirror-gloss, ductile, with low contact resistance, hard.
• the deposits are non-porous, they have good resistance to corrosion and friction.
• the 0.2 to 6 ⁇ m deposit is mirror-gloss, white, ductile, without cracks.
• the deposits are non-porous, they have good resistance corrosion and friction.
• This bath deposits the palladium alloy 80% nickel 20%.
• the deposit of 0.2 to 6 ⁇ m is mirror-gloss, white, ductile, without cracks. Deposits are no porous, they have good resistance to corrosion and friction.
• This bath deposits the palladium alloy 70% - cobalt 30% for application decorative, the deposit of 0.2 to 6 ⁇ m is shiny-mirror, ductile, without cracks.
• the deposits are non-porous, they have good resistance to corrosion and friction.

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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)
• Electrolytic Production Of Metals (AREA)

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• 2000
  • 2000-04-06 FR FR0004381A patent/FR2807450B1/fr not_active Expired - Fee Related
• 2001
  • 2001-04-05 US US10/239,863 patent/US6743346B2/en not_active Expired - Fee Related
  • 2001-04-05 DE DE60102364T patent/DE60102364T2/de not_active Expired - Lifetime
  • 2001-04-05 WO PCT/FR2001/001021 patent/WO2001077417A1/fr active IP Right Grant
  • 2001-04-05 CN CNB01809757XA patent/CN1190522C/zh not_active Expired - Lifetime
  • 2001-04-05 ES ES01921482T patent/ES2220757T3/es not_active Expired - Lifetime
  • 2001-04-05 EP EP01921482A patent/EP1272691B1/fr not_active Expired - Lifetime
  • 2001-04-05 AT AT01921482T patent/ATE262055T1/de not_active IP Right Cessation
  • 2001-04-05 AU AU2001248465A patent/AU2001248465A1/en not_active Abandoned
  • 2001-04-05 JP JP2001575263A patent/JP4790191B2/ja not_active Expired - Fee Related

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