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EP4407067A1 - Composition de bain de placage pour le placage de métal précieux et procédé de dépôt d'une couche de métal précieux - Google Patents

Composition de bain de placage pour le placage de métal précieux et procédé de dépôt d'une couche de métal précieux Download PDF

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Publication number
EP4407067A1
EP4407067A1 EP23153169.0A EP23153169A EP4407067A1 EP 4407067 A1 EP4407067 A1 EP 4407067A1 EP 23153169 A EP23153169 A EP 23153169A EP 4407067 A1 EP4407067 A1 EP 4407067A1
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EP
European Patent Office
Prior art keywords
precious metal
ions
alloys
mmol
plating
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.)
Pending
Application number
EP23153169.0A
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German (de)
English (en)
Inventor
Robert Spreemann
Donny Lautan
Boris Alexander Kraft
Dmytri VOLOSHYN
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.)
Atotech Deutschland GmbH and Co KG
Original Assignee
Atotech Deutschland GmbH and Co KG
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.)
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Publication date
Application filed by Atotech Deutschland GmbH and Co KG filed Critical Atotech Deutschland GmbH and Co KG
Priority to EP23153169.0A priority Critical patent/EP4407067A1/fr
Priority to CN202480008695.XA priority patent/CN120603984A/zh
Priority to TW113102818A priority patent/TW202436687A/zh
Priority to PCT/EP2024/051684 priority patent/WO2024156770A1/fr
Priority to KR1020257024700A priority patent/KR20250139287A/ko
Publication of EP4407067A1 publication Critical patent/EP4407067A1/fr
Pending legal-status Critical Current

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    • 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
    • C23C18/42—Coating with noble metals
    • C23C18/44—Coating with noble metals using reducing agents
    • 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
    • C23C18/1601—Process or apparatus
    • C23C18/1633—Process of electroless plating
    • C23C18/1675—Process conditions
    • C23C18/1683—Control of electrolyte composition, e.g. measurement, adjustment

Definitions

  • the present invention relates to aqueous precious metal plating bath compositions for plating of precious metal layers onto a substrate and a method for depositing precious metal.
  • the plating bath is particularly suitable in the manufacture of printed circuit boards, IC substrates, semiconducting devices, interposers made of glass and the like.
  • Precious metal layers are of paramount interest in the manufacturing of electronic components and in the semiconductor industry.
  • Gold layers are frequently used as solderable and/or wire bondable surfaces in the manufacture of printed circuit boards, IC substrates, semiconducting devices and the like. Typically, they are used as a final finish before soldering and wire bonding.
  • various layer assemblies which are used conventionally in the art.
  • Silver is a cost-efficient replacement for gold in many applications.
  • Electroless plating generally describes methods without using external current sources for reduction of metal ions.
  • Plating processes using external current sources are commonly described as electrolytic or galvanic plating methods.
  • Non-metallic surfaces may be pretreated to make them receptive or catalytic for metal deposition. All or selected portions of a surface may suitably be pretreated.
  • the main components of autocatalytic metal baths are the metal salt, a reducing agent, and, as optional ingredients, a complexing agent, a pH adjuster, and additives, as for example stabilising agents.
  • Complexing agents also called chelating agents in the art
  • Chelating metal renders the metal available to the reducing agent that converts the metal ions to metallic form.
  • a further form of metal deposition is immersion plating.
  • Immersion plating is another deposition of metal using neither external current sources nor chemical reducing agents.
  • the mechanism relies on the substitution of metals from an underlying substrate for metal ions present in the immersion plating solution. This is a distinct disadvantage of immersion plating because deposition of thicker layers is normally limited by the layer porosity.
  • electroless gold plating baths use one or both types of electroless plating. Even if reducing agents have been added to the plating bath, immersion-type plating may occur albeit in a significantly reduced proportion.
  • EP 343 816 A1 discloses an aqueous liquor for use as an electroless gold deposition bath, comprising a source of gold and a reducing agent.
  • This liquor also contains a reduction-stabilising agent selected from a variety of compounds, i.e. mixtures of an alkali metal or ammonium ferrocyanide and an alkali metal or ammonium ferricyanide; 1-H-tetrazole; redox mediators; and mixtures thereof.
  • WO 2017/050662 discloses electroless plating baths and ethylenediamine derivatives as plating bath enhancers.
  • aqueous precious metal plating bath is synonymously named an aqueous solution.
  • aqueous solution means that the prevailing liquid medium, which is the solvent in the solution, is water. Further liquids, that are miscible with water, as for example alcohols and other polar organic liquids, that are miscible with water, may be added. In principle, an aqueous solution comprises more than 50 percent water by weight.
  • the inventive plating baths are electroless precious metal plating baths.
  • Electroless precious metal plating baths comprise different types such as but not limited to immersion-type precious metal plating baths, autocatalytic precious metal plating baths and precious metal plating baths using a mixture of autocatalytic and immersion-type plating and electrolytic plating baths.
  • the inventive precious metal plating baths are autocatalytic precious metal plating baths.
  • Immersion-type precious metal plating baths typically comprise at least the following components: at least one chelating agent; at least one gold source; and at least one pH adjuster.
  • immersion-type precious metal plating baths can comprise additives such as but not limited to at least one grain refiner, at least one wetting agent, and/or at least one accelerator.
  • Autocatalytic precious metal plating baths typically comprise at least the following components: at least one chelating agent; at least one gold source; at least one pH adjuster; at least one reducing agent, and at least one stabilizer.
  • autocatalytic precious metal plating baths can comprise additives such as but not limited to at least one grain refiner, at least one wetting agent, and/or at least one accelerator.
  • the plating bath according to the invention may be prepared by dissolving all components in aqueous liquid medium, preferably in water.
  • the aqueous precious metal plating bath according to the invention comprises at least one source of precious metal ions.
  • the term 'precious metal' shall describe a metal selected from the group consisting of Ru, Rh, Pd, Ag, Os, Ir, Pt, Au. These are the elements in Groups 8 to 11 of Periods 5 and 6 of the Periodic System of the Elements.
  • the precious metal is selected from the group consisting of Au and Ag. More preferred, the precious metal is Au.
  • the concentration of precious metal ions in the aqueous precious metal plating bath according to the invention preferably ranges from 0.5 to 50 mmol/L, more preferably from 1.0 to 30 mmol/L and most preferably from 2.0 to 10 mmol/L. If two or more precious metal ions are contained in the aqueous precious metal plating bath according to the invention the concentration is based on the total amount of substance of precious metal ions.
  • Gold ions can be in either Au + , Au 3+ or both oxidation states.
  • the source of gold ions can be any water soluble gold salt having said oxidation states.
  • the source of gold ions is selected from the group consisting of gold cyanide, gold ammonium cyanide, gold (I) alkali cyanides including gold (I) potassium cyanide, gold (I) sodium cyanide, trisodium gold disulphite, tripotassium gold disulphite and triammonium gold disulphite, gold thiosulphate, gold thiocyanide, gold sulphate, gold chloride, and gold bromide.
  • the source of gold ions is a gold (I) alkali cyanide and may be added to the aqueous plating bath in the form of a solution containing this salt.
  • concentration of gold ions in the aqueous gold plating bath according to the invention preferably ranges from 0.5 to 50 mmol/L, more preferably from 1.0 to 30 mmol/L and most preferably from 2.0 to 10 mmol/L.
  • Silver ions are in the Ag + oxidation state.
  • the source of silver ions can be any water soluble silver salt having said oxidation state.
  • the source of silver ions is selected from the group consisting of silver cyanide [list more silver compounds].
  • the source of silver ions is silver cyanide and may be added to the aqueous plating bath in the form of a solution containing this salt.
  • the concentration of silver ions in the aqueous silver plating bath according to the invention preferably ranges from 0.5 to 50 mmol/L, more preferably from 1.5 to 30 mmol/L and most preferably from 4.0 to 20 mmol/L.
  • cyanide ions form stable complexes with iron (II) ions and/or iron (III) ions.
  • the respective complexes are known as hexacyanoferrate (II) ions and hexacyanoferrate (III), respectively. These are anions bear four (in case of hexacyanoferrate (II)) and three (in case of hexacyanoferrate (III)) negative charges. Typically, these are neutralized by appropriate cations.
  • the source of hexacyanoferrate (II) ions and/or hexacyanoferrate (III) ions can be any water soluble thereof.
  • the source of hexacyanoferrate (II) ions and/or hexacyanoferrate (III) ions is selected from the group consisting of ammonium hexacyanoferrate (II), alkali hexacyanoferrate (II) ions including potassium hexacyanoferrate (II) and sodium hexacyanoferrate (II); ammonium hexacyanoferrate (III), alkali hexacyanoferrate (III) including potassium hexacyanoferrate (III) and sodium hexacyanoferrate (III); and mixtures thereof.
  • the source of hexacyanoferrate (II) ions and/or hexacyanoferrate (III) ions is selected from potassium hexacyanoferrate (II), potassium hexacyanoferrate (III) and mixtures thereof and may be added to the aqueous plating bath in the form of a solution containing this salt.
  • the concentration of hexacyanoferrate (II) ions and/or hexacyanoferrate (III) ions in the aqueous precious metal plating bath according to the invention preferably ranges from 0.1 to 50 mmol/L, more preferably from 0.3 to 30 mmol/L and most preferably from 0.6 to 10 mmol/L.
  • hexacyanoferrate (II) ions and hexacyanoferrate (III) are contained in the aqueous precious metal plating bath according to the invention the concentration is based on the total amount of substance of hexacyanoferrate (II) ions and hexacyanoferrate (III).
  • the source of halogenide can be any water soluble halogenide.
  • the halogenide is bromide and/or iodide.
  • the source of halogenide is selected from the group consisting of ammonium bromide, alkali bromide including potassium bromide, sodium bromide; ammonium iodide, alkali iodide including potassium iodide and sodium iodide; and mixtures thereof.
  • the source of halogenide may be added to the aqueous plating bath in the form of a solution containing this salt.
  • the concentration of halogenide in the electroless aqueous gold plating bath according to the invention preferably ranges from 0.1 to 50 mmol/L, more preferably from 0.3 to 30 mmol/L and most preferably from 1.0 to 10 mmol/L. If two or more halogenide ions are contained in the aqueous precious metal plating bath according to the invention the concentration is based on the total amount of substance of halogenide ions.
  • the concentration of halogenide ions is zero, i.e. no halogenide ions shall be present in the precious metal plating bath.
  • the aqueous precious metal plating bath according to the invention optionally further comprises at least one complexing agent.
  • the optional at least one complexing agent present in the aqueous precious metal plating bath according to the invention is preferably selected from the group consisting of carboxylic acids, hydroxycarboxylic acids, aminocarboxylic acids, diamine carboxylic acids, phosphonic acids, aminophosphonic acids or a salt of the aforementioned.
  • the optional at least one complexing agent serves as a complexing agent for precious metal ions as well as for metal ions dissolved from the substrate during plating, e.g., nickel ions or copper ions.
  • a preferred carboxylic acid is for example oxalic acid or a salt thereof.
  • Preferred hydroxycarboxylic acids are for example tartaric acid, citric acid, lactic acid, malic acid, gluconic acid and salts of the aforementioned.
  • Preferred aminocarboxylic acids are for example glycine, cysteine, methionine and salts of the aforementioned.
  • Preferred diamine carboxylic acids are cyclohexane diamine tetracarboxylic acid (CDTA) and ethylene diamine tetracarboxylic acid (EDTA).
  • a preferred phosphonic acid is 1- hydroxyethane-(1,1,-diphosphonic acid) (HEDP).
  • Preferred aminophosphonic acids are nitrilotri(methylphosphonic acid) (commonly abbreviated as ATMP), diethylenetriaminepentakis(methylphosphonic acid) (commonly abbreviated as DTPMP) and ethylenediaminetetra(methylenphosphonic acid) (commonly abbreviated as EDTMP).
  • ATMP nitrilotri(methylphosphonic acid)
  • DTPMP diethylenetriaminepentakis(methylphosphonic acid)
  • EDTMP ethylenediaminetetra(methylenphosphonic acid)
  • concentration of the optional at least one complexing agent preferably ranges from 0.25 to 250 mmol/L, more preferably from 1.0 to 150 mmol/L.
  • the aqueous precious metal plating bath according to the invention comprises two different complexing agents and/or salts thereof, such as a aminocarboxylic acid or a salt thereof and a phosphonic acid or a salt thereof.
  • the aqueous precious metal plating bath further comprises at least one reducing agent for precious metal ions.
  • the reducing agents for precious metal ions is preferably selected from the group consisting of aliphatic aldehydes such as formaldehyde, acetoaldehyde, propionaldehyde, n-butylaldehyde, ⁇ -methylvaleraldehyde, ⁇ -methylvaleraldehyde, ⁇ -methylvaleraldehyde or the like; aliphatic dialdehydes such as glyoxal, succindialdehdye or the like; aliphatic unsaturated aldehydes such as croton aldehyde or the like; aromatic aldehydes such as benzaldehyde, o-nitrobenzaldehyde, m-nitrobenzaldehyde, p-nitrobenzaldehyde, o-tolaldehyde, m-tolaldehyde, p-tolaldehyde, o-hydroxybenzaldehyde,
  • source of glyoxylic acid encompasses glyoxylic acid and all compounds that can be converted to glyoxylic acid in aqueous solution.
  • aqueous solution the aldehyde containing acid is in equilibrium with its hydrate.
  • a suitable source of glyoxylic acid is dihaloacetic acid, such as dichloroacetic acid, which will hydrolyse in an aqueous medium to the hydrate of glyoxylic acid.
  • An alternative source of glyoxylic acid is the bisulphite adduct as is a hydrolysable ester or other acid derivative. The bisulphite adduct may be added to the electroless aqueous gold plating bath according to the invention or formed in situ.
  • the bisulphite adduct may be made from glyoxylate and either bisulphite, sulphite or metabisulphite.
  • Formaldehyde, sources of glyoxylic acid and glyoxylic acid are preferred, most preferred is formaldehyde.
  • the concentration of the at least one reducing agent for precious metal ions preferably ranges 0.1 to 500 mmol/L, more preferably 1 to 300 mmol/L, even more preferably 2 to 200 mmol/L and most preferably from 5 to 100 mmol/L.
  • a wetting agent is a surface-active molecule used to reduce the surface tension of water. While a number of wetting agents and how they are applied are known to the skilled person, a preferred wetting agent is ethylene glycole.
  • the concentration of the at least one wetting agent for precious metal ions preferably ranges from 0,02 to 9,0 mol/L, more preferably 0,2 to 5,4 mol/L, even more preferably 1,0 to 3,6 mol/L.
  • the aqueous precious metal plating bath according to the invention optionally comprises an accelerator which is selected from the group consisting of thallium ions, arsenic ions, selenium ions and lead ions.
  • an accelerator which is selected from the group consisting of thallium ions, arsenic ions, selenium ions and lead ions.
  • Such crystal adjuster is preferably added to the electroless aqueous precious metal plating bath according to the invention in a concentration range of 0.00005 to 0.5 mmol/L, more preferably 0.0001 to 0.25 mmol/L and most preferably from 0.00015 to 0.1 mmol/L.
  • Useful sources for said ions can be water-soluble salts thereof such as the respective nitrates, sulphates and halides.
  • inventive precious metal plating bath can comprise further components such as, but not limited to, one or more stabilizing agents, and/or one or more plating enhancers
  • the electroless aqueous gold plating bath according to the invention optionally comprises at least one stabilising agent selected from the group consisting of sources of cyanide ions, hydantoin and alkyl derivatives thereof such as alkylhydantoin and dialkylhydantoin wherein alkyl residues in this context comprise C 1 to C 8 alkyls, preferably methyl, which can be cyclic and/or alicyclic, branched or unbranched, sulphur compounds such as 2-mercaptobenzothiazole, 2-mercaptobenzoimidazole, mercaptoacetic acid, 3-(2-benz-thiazolylthio)-1-propanesulphonic acid, mercaptosuccinic acid, thiosulphuric acid, thioglycol, thiourea, thiomalic acid and the like, and aromatic nitrogen compounds such as benzotriazole, 1,2,4-aminotriazole and the like.
  • the inventive plating solution does not comprise stabilizing agents selected from cyanide ions.
  • Such cyanide ion stabilizing agents contain cyanide ions in free form. Even though it is evident, it is stated that hexacyanoferrate compounds do not fall under this definition since the cyano group ligands form highly stable complexes with the iron core.
  • inventive plating baths can comprise at least one stabilizing agent selected from cyanide ions.
  • the concentration of the optional stabilising agent can be selected dependant on its chemical structure and can be determined in routine experiments by anyone known in the art.
  • the concentration of the optional stabilising agent preferably ranges 0.0001 to 200 mmol/L, it ranges more preferably from 0.001 to 125 mmol/L and most preferably from 0.01 to 75 mmol/L.
  • Such stabilising agents are conventionally added to electroless gold plating baths to improve their lifetime and to prevent plate-out.
  • two or more stabilising agents are used. More preferably, a source of cyanide ions in a concentration of 0.0003 to 5 mmol/L and one or more of hydantoin and alkyl derivatives thereof in a concentration of 1 to 200 mmol/L, more preferably from 10 to 125 mmol/L and most preferably from 20 to 75 mmol/L and/or sulphur compounds in a concentration of 0.001 to 50 mmol/L, more preferably from 0.001 to 30 mmol/L and most preferably from 0.001 to 20 mmol/L is selected.
  • the inventive plating baths can further comprise at least one ethylenediamine derivative of formula (I) as disclosed in WO 2017/050662 as plating bath enhancers.
  • the ethylenediamine derivative according to formula (I) will be referred to herein as plating enhancer compound.
  • the plating enhancer compound according to formula (I) bears the residues R 1 and R 2 which comprise 2 to 12 carbon atoms and are selected from the group consisting of branched alkyl, unbranched alkyl, cycloalkyl or combinations thereof wherein the individual residues R 1 and R 2 are the same or different.
  • the amine moieties in the plating enhancer compound of formula (I) are secondary amine moieties.
  • the residues R 1 and R 2 of the plating enhancer compound of formula (I) comprise 2 to 8 carbon atoms, more preferred 2 to 6 carbon atoms, even more preferred 2 to 4 carbon atoms.
  • residues R 1 and R 2 in formula (I) are the same.
  • the alkyl residues R 1 and R 2 in formula (I) are free of terminal hydroxy moieties (-OH).
  • residues R 1 and R 2 in formula (I) are free of terminal primary amino moieties.
  • residues R 1 and R 2 are free of any further amino moieties and/or any hydroxy moieties. It is even more preferable that the alkyl residues are free of substituents and consist of carbon and hydrogen atoms only.
  • the plating enhancer compound from the following group consisting of N 1 ,N 2 -diethylethane-1,2-diamine, N 1 ,N 2 -dipropylethane-1,2-diamine, N 1 ,N 2 -di- iso -propylethane-1,2-diamine, N 1 ,N 2 -dibutylethane-1,2-diamine, N 1 ,N 2 - di -iso- butylethane-1,2-diamine, N 1 ,N 2 -di- tert -butylethane-1,2-diamine, N 1 ,N 2 -dipentylethane-1,2-diamine, N 1 ,N 2 -di- iso -pentylethane-1,2-diamine, N 1 ,N 2 -di- sec -pentylethane-1,2-diamine, N 1 ,N 2 -di- tert
  • R 1 and R 2 are branched alkyl residues having 3 to 6 carbon atoms.
  • the concentration of the at least one plating enhancer compound according to formula (I) in the aqueous precious metal plating bath according to the invention preferably ranges from 0,5 - 1000 mmol/L, more preferably from 1 to 200 mmol/L, even more preferably from 5 to 75 mmol/L and most preferably from 10 to 50 mmol/L. If more than one plating enhancer compound is contained in the aqueous precious metal plating bath according to the invention the concentration is based on the total amount of substance of all plating enhancer compounds.
  • the electroless aqueous precious metal plating bath according to the invention is free of intentionally added second sources of reducible metal ions (disregarding trace of impurities commonly present in technical raw materials) allowing for pure precious metal deposits to be formed.
  • Pure precious metal deposits are soft, malleable, and particularly suitable for wire bonding and soldering. Traces of impurities are understood as compounds present in a technical raw material of 1 wt.-% or less.
  • the pH of the electroless aqueous precious metal plating bath according to the invention preferably ranges from 5 to 10, more preferably from 7 to 9, even more preferably from 8 to 9.
  • the target pH value is adjusted by using for example acids such as phosphoric acid or bases such as sodium hydroxide or potassium hydroxide. It is advantageous and thus preferable to continuously control and adjust the pH value during plating as this also improves the plating bath lifetime.
  • the method for depositing a precious metal layer onto a substrate comprising, in this order, the steps
  • This contacting is preferably accomplished by dipping the substrate or the at least a portion of the surface of substrate into the plating bath or by spraying the plating bath onto the substrate or onto the at least a portion of surface of the substrate.
  • the at least a portion of the surface of the substrate preferably consists of a metal or metal alloy and precious metal is then deposited onto the at least a portion of the surface of the substrate consisting of a metal or metal alloy, selected from the group consisting of nickel, nickel alloys such as nickel phosphorous alloys, nickel boron alloys, cobalt, cobalt alloys such as cobalt phosphorous alloys, cobalt molybdenum phosphorous alloys, cobalt molybdenum boron alloys, cobalt molybdenum boron phosphorous alloys, cobalt tungsten phosphorous alloys, cobalt tungsten boron alloys, cobalt tungsten boron phosphorous alloys, palladium, palladium alloys such as palladium phosphorous alloys, palladium boron alloys, copper and copper alloys and precious metal or precious metal alloys.
  • the aqueous precious metal plating bath according to the invention can be used to deposit precious metal layers on precious
  • the substrates can be pretreated prior to plating, as it is known in the art.
  • Such pretreatment includes cleaning steps with solvents and/or surfactants to remove mostly organic contaminants, etching steps with acids and optionally, oxidising or reducing agents to remove oxides and activation steps.
  • the latter are to deposit a noble metal on the surface or a part thereof to make it more receptive for plating.
  • noble metal can be palladium which can be deposited as a salt before it is reduced to elementary palladium on the surface. Or it can be deposited in a colloidal form and - where appropriate - be subjected to an acceleration step with an acid such as hydrochloric acid to remove any protective colloids such as tin colloids.
  • Such an activation layer normally is not a discrete layer but an aggregation of island structures of palladium. However, activation layers are considered as metal substrates in the context of the present invention.
  • the plating baths of the inventive method are electroless precious metal plating baths.
  • Electroless precious metal plating baths comprise different types such as but not limited to immersion-type precious metal plating baths, autocatalytic precious metal plating baths and precious metal plating baths using a mixture of autocatalytic and immersion-type plating and electrolytic plating baths.
  • the precious metal plating baths of the inventive method are autocatalytic precious metal plating baths.
  • the temperature of the aqueous precious metal plating bath according to the invention is preferably in the range of 30 to 95 °C, more preferably from 70 to 90 °C, even more preferably from 75 to 85 °C, yet even more preferably from 77 to 84 °C during plating.
  • the plating time is preferably in the range of 1 to 60 min, more preferably in the range of 5 to 30 min. However, if thinner or thicker deposits are desired, the plating time can be outside above-described ranges and adjusted accordingly.
  • components which are being used during plating.
  • Such components are inter alia the source of precious metal ions, the reducing agent for precious metal ions, the at least one stabilising agent and the plating enhancer compound.
  • the pH value can be adjusted continuously or in intervals as well.
  • the aqueous precious metal plating bath according to the invention may be used with horizontal, vertical and spray plating equipment.
  • the aqueous precious metal plating baths according to the invention allows for sufficient plating rates (deposited thickness of the plated metal layer over time) (see examples2 to 4). Most plating baths known in the art which are somewhat stable do not allow for sufficient plating rates.
  • the aqueous precious metal plating baths according to the invention form homogeneous precious metal deposits with little layer thickness diversion.
  • the standard deviation of the precious metal layer thickness is below 10% or even below 8%. This little deviation is advantageously achievable even when plating on various substrates having different sizes.
  • Pro Select S8, MicroEtch C, Aurotech ® Pre Dip, Aurotech ® Activator 1000, Aurotech ® CNN mod and PD-Tech ® PC 1 are products available from Atotech GmbH.
  • the source of gold ions was in all cases K[Au(CN) 2 ].
  • the source of silver ions was K[Ag(CN) 2 ].
  • Printed circuit test boards having a multitude of copper pads of different sizes ranging from 0.25 to 49 mm 2 on one side were used in all experiments as substrates. They were cleaned and etched prior to activation with palladium. Then, nickel was deposited on the copper surfaces for ENIG or nickel/palladium for ENEPIG before the gold layer was plated thereon. The individual pads had the following areas 1: 0.25 mm 2 , 2: 1 mm 2 , 3: 4 mm 2 , 4: 9 mm 2 , 5: 25 mm 2 , 6: 49 mm 2 .
  • the deposit thickness was measured at 6 pads on one side of the test boards.
  • the chosen copper pads had different sizes and are used to determine the layer thickness by XRF using the XRF instrument Fischerscope XDV-SDD (Helmut Fischer GmbH, Germany).
  • XRF instrument Fischerscope XDV-SDD Helmut Fischer GmbH, Germany.
  • the plating rate was calculated by dividing the obtained layer thickness by the time necessary to obtain said layer thickness.
  • the layer thickness homogeneity expressed as Coefficient of Variation (COV) was determined as the standard deviation from the average thickness value. In case of gold, this term is abbreviated as Au COV.
  • Gold plating baths containing the following components were prepared by dissolution of all components in water: Table 1: 1 2 3 4 5 6 7 8 9 10 ( Ref) potassium hydroxide to adjust pH to range from 7.0 to 7.2 x x x x x x x x x x x x plating enhancer compound (mmol/L) (50) (50) (50) (50) (50) (50) (50) (50) (50) (50) (50) (50) complexing agent (mmol/L) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89) EDTA (89)
  • Gold plating baths containing the following components were prepared by dissolution of all components in water: Table 2: 1 2 3 4 5 6 7 8 potassium hydroxide to adjust pH to range from 7.1 to 9.0 7.1 9.0 7.1 9.0 9.0 7.1 9.0 9.0 9.0 9.0 9.0 plating enhancer compound (mmol/L) (70) (20) (70) (20) (20) (20) complexing agent (mmol/L) EDTA (89) EDTA (89) EDTA (14) EDTA (14) CDTA (89) CDTA (89) EDDS (89) EDTMP (89) 5,5-dimethylhydantoin (mol/L) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47) (47)
  • a substrate was subjected to the following process steps (Table A) by dipping the substrates into the respective solutions employing the given parameters: Table A: Process sequence for gold plating.
  • a substrate was subjected to the process steps described in Table A of Example 2 by dipping the substrates into the respective solutions: After this process sequence the thicknesses of the individual metal layers were measured. The plating rate was calculated as described above.
  • Gold plating baths containing the following components were prepared by dissolution of all components in water: Table 4: 1 2 3 4 5 6 7 8 9 potassium hydroxide to adjust pH to range from 8.8 to 9.2 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 plating enhancer compound (mmol/L) (20) (20) (20) (20) (20) (20) (20) (20) (20) (20) complexing agent (mmol/L) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) CDTA (25) Auxiliary complexing agent (mmol/L) EDDS (25) HEDTA (25) Iminodiacetic acid (2
  • a substrate was subjected to the process steps described in Table A of Example 2 by dipping the substrates into the respective solutions: After this process sequence the thicknesses of the individual metal layers were measured. The plating rate was calculated as described above.
  • Gold plating baths containing the following components were prepared by dissolution of all components in water: Table 5: 1 2 3 4 5 6 7 8 potassium hydroxide to adjust pH to range from 8.8 to 9.2 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 plating enhancer compound (mmol/L) (20) (20) (20) (20) (20) (20) (20) (20) complexing agent (mmol/L) CDTA (15) CDTA (15) CDTA (15) CDTA (15) CDTA (15) CDTA (15) CDTA (15) CDTA (15) CDTA (15) Auxiliary complexing agent (mmol/L) HEDP (75) HEDP (75) HEDP (75) HEDP (75) HEDP (75) HEDP (75) HEDP (75) HEDP (75) HEDP (75) HEDP (75) Glycols (mol/L) Ethylene glycol (2.7) Diethylene glycol (1,3) Polyethylene glycol 200 (0,7) Polyethylene glyco
  • a substrate was subjected to the process steps described in Table A of Example 2 by dipping the substrates into the respective solutions: After this process sequence the thicknesses of the individual metal layers were measured. The plating rate was calculated as described above.

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  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
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  • Chemically Coating (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
  • Electroplating Methods And Accessories (AREA)
EP23153169.0A 2023-01-24 2023-01-24 Composition de bain de placage pour le placage de métal précieux et procédé de dépôt d'une couche de métal précieux Pending EP4407067A1 (fr)

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EP23153169.0A EP4407067A1 (fr) 2023-01-24 2023-01-24 Composition de bain de placage pour le placage de métal précieux et procédé de dépôt d'une couche de métal précieux
CN202480008695.XA CN120603984A (zh) 2023-01-24 2024-01-24 用于电镀贵金属的电镀浴组合物以及沉积贵金属层的方法
TW113102818A TW202436687A (zh) 2023-01-24 2024-01-24 用於電鍍貴金屬之電鍍浴組合物以及沉積貴金屬層之方法
PCT/EP2024/051684 WO2024156770A1 (fr) 2023-01-24 2024-01-24 Composition de bain de placage pour placage de métal précieux et procédé de dépôt d'une couche de métal précieux
KR1020257024700A KR20250139287A (ko) 2023-01-24 2024-01-24 귀금속의 도금을 위한 도금욕 조성물 및 귀금속 층을 침착시키기 위한 방법

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0343816A1 (fr) 1988-05-25 1989-11-29 Engelhard Corporation Procédé de dépôt chimique
US20160145745A1 (en) * 2014-11-24 2016-05-26 Rohm And Haas Electronic Materials Llc Formaldehyde-free electroless metal plating compositions and methods
WO2017050662A1 (fr) 2015-09-21 2017-03-30 Atotech Deutschland Gmbh Composition de bain de placage pour dépôt autocatalytique d'or et procédé de dépôt d'une couche d'or
US20180340261A1 (en) * 2015-11-27 2018-11-29 Atotech Deutschland Gmbh Plating bath composition and method for electroless plating of palladium

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0343816A1 (fr) 1988-05-25 1989-11-29 Engelhard Corporation Procédé de dépôt chimique
US20160145745A1 (en) * 2014-11-24 2016-05-26 Rohm And Haas Electronic Materials Llc Formaldehyde-free electroless metal plating compositions and methods
WO2017050662A1 (fr) 2015-09-21 2017-03-30 Atotech Deutschland Gmbh Composition de bain de placage pour dépôt autocatalytique d'or et procédé de dépôt d'une couche d'or
US20180340261A1 (en) * 2015-11-27 2018-11-29 Atotech Deutschland Gmbh Plating bath composition and method for electroless plating of palladium

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
VRUBLEVSKAYA O N ET AL: "ELECTROLESS GOLD PLATING FROM TETRACHLOROAURATE SOLUTIONS CONTAINING HEXACYANOFERRATE(II) IONS", TRANSACTIONS OF THE INSTITUTE OF METAL FINISHING, MANEY PUBLISHING, BIRMINGHAM, GB, vol. 85, no. 5, 1 September 2007 (2007-09-01), pages 254 - 259, XP001507661, ISSN: 0020-2967, DOI: 10.1179/174591907X229662 *

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TW202436687A (zh) 2024-09-16

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