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 electrolyte for the electrodeposition of palladium or palladium alloys on metallic or conductive substrates.
• this is a Pd electrolyte containing optionally further metals and an organic oligoamine as a complexing agent, with the alloy coatings with e.g. 80% Pd for technical and decorative applications can be deposited.
• the invention is directed to a corresponding galvanotechnisches method using this electrolyte and special, advantageously usable for this process palladium salts.
• the electrodeposition of palladium or palladium alloys on metallic substrates has a variety of decorative and technical applications.
• Galvanically deposited pure palladium and palladium-nickel layers, possibly with gold flash each, are recognized materials eg for low-current contacts or plug-in contacts (eg on circuit boards) and can be considered as a substitute for hard gold [ Galvanotechnik 5 (2002), 1210ff, Simon u. Yasumura: "Galvanic palladium coatings for technical applications in electronics "Palladium deposits with very small layer thickness on so-called lead frames in semiconductor production can also replace the silver used in the bond area [ Galvanotechnik 6 (2002), 1473ff, Simon u. Yasumura: "Galvanic palladium coatings for technical applications in electronics "].
• pyridines mentioned by name are 1- (3-sulfopropylpyridinium betaine and 1- (2-hydroxy-3-sulfopropylpyridinium betaine). The latter two substances have, according to the authors, a negative effect on the gloss of the resulting coatings.
• a method according to the US6743346 also uses ethylenediamine as a complexing agent and brings the palladium in the form of the solid compound of palladium sulfate and ethylenediamine.
• the salt contains 31 to 41% palladium (mole ratios [SO 4 ]: [Pd] between 0.9 and 1.15 and [ethylenediamine]: [Pd] between 0.8 and 1.2). It is not soluble in water, but dissolves in the electrolyte with excess ethylenediamine ( Plating & Surface Finishing, (2007) 4, pp. 26-35, St.
• Palladium hydroxide complexes are disclosed for their application in electrolytic coating baths.
• these compounds may comprise oligoamines.
• brightener systems based on internal salts can be used.
• the US 5178745 refers to acid palladium electrolytes, which has as a complexing agent a compound selected from the group of organic diamines. It is required that the electrolyte should contain an adequate amount of chloride ions.
• An electrolytic coating solution which contains palladium in the form of its soluble complexes with, inter alia, organic polyamines.
• the bath may have internal salts, but usually works at an acidic pH.
• the US 20030047460 refers to new complex salts of palladium sulfate and ethylenediamine.
• the three components should be present in a certain ratio to each other in the bathroom. This electrolytic bath also works at an acidic pH.
• Object of the present invention was in the context of the cited prior art, the indication of a further electrolyte and working with this electrolyte process, which help overcome the disadvantages mentioned.
• the specified electrolyte composition or the corresponding method should help to produce glossy surfaces even at high current densities and fast electrolysis processes, which would be particularly advantageous from an economic and ecological point of view.
• aqueous electrolyte for the electrodeposition of palladium or a palladium alloy on a metallic or conductive substrate, which to be deposited, complexed with organic oligoamines metal ions in the form of their salts with oxide hydroxide, hydroxide, bicarbonate and / or carbonate as Having counterions and a brightener based on an inner salt of a quaternary ammonium and a sulfonic acid group, one arrives in a surprisingly simple manner and successfully to solve the problem.
• the electrolyte according to the invention or by using the method according to the invention it is now possible to produce the desired shiny surfaces with qualitatively excellent results both at low and at high current densities.
• the electrolyte composition according to the invention is in no way suggested by the prior art.
• the electrolyte according to the invention makes it possible to deposit the palladium alone or in the form of an alloy associated with other metals.
• Other metals that can be used in the art for this purpose in question. These may be e.g. Nickel, cobalt, iron, indium, gold, silver or tin or mixtures thereof.
• the metal ions to be deposited are selected from the group consisting of nickel, cobalt, iron and mixtures thereof.
• the electrolyte contains these metals in the form of their soluble salts.
• Suitable salts are preferably those selected from the group of phosphates, carbonates, bicarbonates, hydroxides, oxides, sulfates, sulfamates, alkanesulfonates, pyrophosphates, phosphonates, nitrates, carboxylic acid salts and mixtures thereof.
• the person skilled in the art selects the concentrations of the metals to be used in the electrolyte on the basis of his general technical knowledge. It has been found that advantageous results can be achieved if palladium is used in concentrations of 1-100 g / L, preferably 2-70 g / L, and more preferably 4-50 g / L and most preferably 5-25 g / L is present based on the electrolyte.
• the further metal ions to be deposited can be found in concentrations of ⁇ 50 g / L based on the electrolyte.
• concentration of these ions in the electrolyte is preferably ⁇ 40 g / L, more preferably ⁇ 30 g / L, based on the electrolyte.
• a uniform deposition of the metal ions under the conditions according to the invention is advantageous, inter alia, if they are complexed.
• Suitable oligonucleotides for these complexes have proven to be organic oligoamines.
• Advantageous is the use of polydentate, in particular ligands based on di-, tri- or tetraamines. Particularly preferred are those having 2 to 11 carbon atoms.
• ligands selected from the group consisting of ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,2-propylenediamine, trimethylenetetramine, hexamethylenetetramine.
• EDA ethylene diamine
• oligoamines used in the estimation of the amount. In the estimation of the amount, he will orientate himself by the fact that a sufficient amount must be present in order to obtain as even as possible a deposition of the palladium or of the palladium alloy. On the other hand, at least economic considerations limit the use of large quantities of oligoamines.
• An amount of 0.1-5 mol / L of oligoamines in the electrolyte is advantageous. More preferably, the concentration is in the range between 0.3-3 mol / L. Most preferably, the concentration of oligoamines at 0.5 - 2 mol / L electrolyte.
• the pH of the electrolyte according to the invention can be adjusted according to the skilled person for the particular application in the acidic to neutral range.
• a further preferred range is from pH 3.5 to pH 6.5, more preferably from pH 4 to pH 6, and most preferably around pH 5 to pH 5 ; 5.
• the electrolyte according to the invention has brighteners based on an internal salt of a quaternary ammonium and an acid group.
• a quaternary ammonium compound is preferably one in which the positively charged nitrogen atom is part of an aromatic ring system.
• molecular components those skilled in the art are especially those which concern a or polynuclear aromatic systems, such as pyridinium, pyrimidinium, pyrazinium, pyrrolinium, imidazolinium, thiazolinium, indolinium, carbazolinium derivatives or such substituted systems in consideration. Very particular preference is given to pyridinium- or alkyl- or alkenyl-substituted pyridinium derivatives used. Most preferred is the selection of a brightener having as a molecular constituent a quaternary ammonium compound based on a pyridinium derivative.
• the brightener contains an acid group, so that in the present case the brightener is an internal salt or a betaine.
• the term "acid group” refers to a group which, under the given conditions, is present predominantly in the deprotonated form in the electrolyte.
• the acid group may be derived from those selected from the group consisting of phosphoric acid, phosphonic acid, sulfuric acid, sulfonic acid, carboxylic acid. Particularly preferred is the sulfonic acid as part of the brightener.
• the acid group and the quaternary ammonium moiety of the brightener may be linked by (C 1 -C 8 ) -alkylene, (C 1 -C 8 ) -alkenylene, (C 6 -C 18 ) -arylene, which may optionally be substituted be.
• (C 1 -C 8 ) -alkylene (C 1 -C 8 ) -alkenylene, (C 6 -C 18 ) -arylene, which may optionally be substituted be.
• those selected from the group consisting of 1- (3-sulfopropyl) -2-vinylpyridinium betaine), 1- (3-sulfopropylpyridinium betaine and 1- (2-hydroxy-3-sulfopropylpyridinium betaine) have been found.
• the brightener can be used in quantities which are obvious to a person skilled in the art.
• An upper limit is the amount of brightener, in which the cost of its use is no longer justified by the effect achieved.
• the use of the brightener is thus advantageous in amounts of from 1 to 10000 mg / L of electrolyte.
• the brightener is used in a concentration of 5 to 5000 mg / L of electrolyte, most preferably in an amount of 10 to 1000 mg / L of electrolyte.
• the electrolyte according to the invention may contain further constituents which have a positive influence with regard to the bath stability, the deposition behavior of the metals, the quality of the deposited material and the electrolysis conditions.
• those skilled in the art in particular means for reducing the internal stresses of the coating, wetting agents, conductive salts, other brighteners and / or buffer substances, etc. into consideration.
• wetting agents may be selected from the following groups consisting of anionic wetting agents such as sodium lauryl sulfate, dodecylbenzenesulfonate sodium salt, sodium dioctylsulfosuccinate, nonionic wetting agents such as polyethylene glycol fatty acid esters and / or cationic wetting agents such as cetyltrimethylammonium bromide can be used.
• anionic wetting agents such as sodium lauryl sulfate, dodecylbenzenesulfonate sodium salt, sodium dioctylsulfosuccinate
• nonionic wetting agents such as polyethylene glycol fatty acid esters and / or cationic wetting agents such as cetyltrimethylammonium bromide can be used.
• Conducting salts selected from the group consisting of potassium sulfate or sodium sulfate, phosphate, nitrate, alkanesulfonate, sulfamate and mixtures thereof can advantageously be used to improve the conductivity and throwing power of the electrolyte.
• buffer substances are those selected from the group consisting of boric acid or phosphates or a carboxylic acid and / or salts thereof, such as e.g. Acetic acid, citric acid, tartaric acid, oxalic acid, succinic acid, malic acid, lactic acid, phthalic acid.
• brightener additives may advantageously those selected from the group consisting of N, N-diethyl-2-propyne-1-amine, 1,1-dimethyl-2-propynyl-1-amine, 2-butyne-1,4-diol, 2-butyne-1,4-diol ethoxylate, 2-butyne-1,4-diol propoxylate, 3-hexyne-2,5-diol and sulfopropylated 2-butyne-1,4-diol or one of their salts.
• Further base gloss agents may be allylsulfonic acid and / or vinylsulfonic acid and / or propargylsulfonic acid or their alkali metal salts in quantities of from 0.01 to 10 g / l of electrolyte.
• those selected from the group consisting of iminodisuccinic acid and / or sulfamic acid and / or sodium saccharinate may be advantageously used.
• the present invention also provides a process for the electrodeposition of palladium or a palladium alloy on a metallic or conductive substrate, wherein an electrolyte according to the invention is used.
• the palladium or palladium alloy may be electrodeposited on substrates well known to those skilled in the art for this purpose.
• the metallic or electrically conductive substrates are selected from the group consisting of nickel, nickel alloys, gold, silver, copper and copper alloys, iron, iron alloys.
• nickel or copper or copper alloy is coated with the palladium- or palladium-containing layer according to the invention. But even conductive plastics can be coated according to the invention with this method.
• the temperature in the electrolytic deposition can be chosen arbitrarily by the expert.
• the temperature is set at which a corresponding desired deposition can take place. This is the case at temperatures of 20 ° C to 80 ° C.
• a temperature of 30 ° C to 70 ° C and most preferably from 40 ° C to 60 ° C is set.
• the current density to be set can be selected by the person skilled in the art according to the underlying electrolysis arrangement during the electrolysis according to the invention.
• the current densities are preferably between 0.1 and 150 A / dm 2 . Particularly preferred are 0.1-10.0 A / dm 2 for drum and rack applications and 5.0-100 A / dm 2 for high speed applications. Most preferably, 5.0-70 A / dm 2 is set for high-speed applications, and 0.2-5 A / dm 2 is most preferred in drum and rack applications.
• the inventive method is advantageously carried out so that the deposition is carried out using non-soluble anodes.
• non-soluble anodes particularly preferred is the use of insoluble anodes of platinized titanium or mixed oxide anodes. These are most preferably non-soluble anodes of platinized titanium or iridium / ruthenium / tantalum oxide coated titanium or niobium or tantalum.
• Anodes made of graphite or of durable stainless steel are also possible.
• the subject matter of the present invention is likewise a special palladium salt which can advantageously be used and adapted for the process according to the invention.
• These are a palladium complex compounds consisting of a divalent palladium cation, one or more di-, tri- or tetradentate organic amine ligands and carbonate or two bicarbonate or hydroxide anions or a mixture thereof.
• the advantage here is the use of multidentate ligands based on di-, tri or tetraamines. Particularly preferred are those having 2 to 11 carbon atoms.
• ligands selected from the group consisting of ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,2-propylenediamine, trimethylenetetramine, hexamethylenetetramine.
• EDA ethylene diamine
• the reaction temperature is preferably between 20 and 95 ° C, more preferably between 40 and 90 ° C, most preferably between 60 and 80 ° C.
• an electrolyte of the invention described herein with, for example, 20 g / l of palladium as bis (ethylenediamino) -palladium (II) hydrogen carbonate, 16 g / l of nickel as nickel (II) sulfate and 50 g / l of ethylenediamine enable the brighteners 1- (3 Sulfopropylpyridinium betaine or 1- (2-hydroxy-3-sulfopropylpyridinium betaine in amounts of 50 to 500 mg / l, especially in the low current density range, the deposition of high-gloss coatings.
• 2-hydroxy-3-sulfopropylpyridinium betaine in higher concentrations up to 2 g / L electrolyte extends the applicable current density range, so it is possible to apply current densities of up to 100 A / dm 2 in the described electrolyte for high-speed deposition.
• Ammonia and chloride are also avoided with the new palladium-nickel electrolyte based on ethylenediamine, which significantly reduces the risk potential and the unpleasant odor for humans and plant corrosion.
• the disadvantages of the previous, ammonium and chloride-free ethylene-diamine based processes are avoided.
• the use of carbonate or bicarbonate as counter ions to palladium and nickel allows an extension of the service life.
• the anions used are not stable in the applied pH range between, for example, 3 and 5.5 and decompose immediately upon addition of the metal salt to carbon dioxide and hydroxide. The volatile CO 2 escapes from the electrolyte and thus does not contribute to increasing the bath density.
• the pH in the electrolyte drops slightly, which compensates for the alkaline effect of hydroxide ions formed on decomposition of carbonic acid.
• the pH during operation remains surprisingly automatically constant by adding further palladium salts according to the invention.
• the bath density gradually increased until finally the salinity reached a maximum value and the electrolyte is no longer stable.
• the indicated constituents of the electrolyte are dissolved in 4 L of deionized water. Subsequently, the palladium or the palladium alloy is deposited on a brass sheet under the given electrolysis conditions.
• An electrolyte for depositing PdNi layers with 80% by weight of palladium may be e.g. have the following composition:
• the raised coatings (2 ⁇ m) are homogeneously bright, ductile, crack-free in the mentioned current density range and have a relatively constant Pd content of 80 to 83%.
• the resulting coatings (2 microns) are homogeneously high gloss in the current density range mentioned, brilliant-bright, very ductile, crack-free and have a relatively constant Pd content of 80 to 83%.
• Mass [g] Amount of substance [mol] Molecular weight [g / mol] Density [g / cm 3 ] Volume [ml] palladium 100 * 0.940 106.4 - - Ethylenediamine (EDA) 117 1,947 60.1 0,898 130 * 277 g of tetraamminepalladium (II) bicarbonate TAPHC (36% Pd)
• Tetraamminepalladium (II) bicarbonate (product # 45082) from Alfa Aesar Ethylene diamine 99% for synthesis (e.g., Merck # 800947)

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• 2008
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