Electrolytic solution for electrochemical deposition gold and its alloys

Abstract

An aqueous electrolytic solution for electrochemical deposition of gold or its alloys includes at least a soluble gold compound designed for electrolytic deposition and, optionally at least a secondary metal compound designed for co-deposition in the form of a gold alloy. The solution includes 0.3 to 3 moles per mole of gold contained in the electrolytic solution of an organic compound having one or two aldehyde functions, this organic compound being or an organic compound having 3 to 20 carbon atoms and one or two aldehyde functions in the form of a saturated or unsaturated, linear or branched aliphatic group, or a group containing at least a saturated, unsaturated or aromatic cycle. The organic compound may further include at least a heteroelement selected among oxygen, nitrogen, sulfur and phosphorus or be in the form of a salt, in particular a sulphonate. The presence of the organic compound enables increasing the speed of electrodeposition and/or decreasing contact resistance.

1 . An aqueous electrolytic bath for electrochemically depositing gold or its alloys comprising at least one soluble gold compound intended to be deposited electrolytically and, optionally, at least one secondary metal compound intended to be co-deposited in the form of an alloy with gold, characterised in that it further comprises 0.3 to 3 moles, per mole of gold contained in the electrolytic bath, of an organic compound comprising one or two aldehyde functions, said organic compound being: 
 either glyoxal, or    an organic compound having 3 to 20 carbon atoms and one or two aldehyde functions in the form:    of a linear, branched, saturated or unsaturated aliphatic group, or    of a group containing at least one saturated, unsaturated or aromatic ring,    it being possible for said organic compound to further comprise at least one heteroelement selected from the group consisting of oxygen, nitrogen, sulphur, and phosphorus, or to be in the form of a salt, particularly in the form of a sulphonate.    
     
     
         2 - 22 . (canceled)  
     
     
         23 . An aqueous electrolytic bath for electrochemically depositing gold or its alloys comprising at least one soluble gold compound intended to be deposited electrolytically and, optionally, at least one secondary metal compound intended to be co-deposited in the form of an alloy with gold, the bath further comprising 0.3 to 3 moles, per mole of gold contained in the electrolytic bath, of an organic compound comprising one or two aldehyde functions, said organic compound being an organic compound having 3 to 20 carbon atoms and one or two aldehyde functions in the form: 
 of a linear, branched, saturated or unsaturated aliphatic group, or    of a group containing at least one saturated, unsaturated or aromatic ring,    said organic compound optionally further comprising at least one heteroelement selected from the group consisting of oxygen, nitrogen, sulfur, and phosphorus, or optionally being in the form of a salt.    
     
     
         24 . The electrolytic bath according to  claim 23 , which contains 1.5 to 2.5 moles of said organic compound comprising one or two aldehyde functions per mole of gold.  
     
     
         25 . The electrolytic bath according to  claim 23 , wherein said organic compound is an aldehyde of formula R—CHO in which R is a linear or branched, saturated or unsaturated aliphatic group having 3 to 12 carbon atoms.  
     
     
         26 . The electrolytic bath according to  claim 23 , wherein said organic compound has 4 to 20 carbon atoms and comprises at least one saturated, unsaturated or aromatic ring, or is a salt thereof.  
     
     
         27 . The electrolytic bath according to one of a  claim 23 , wherein said organic compound has 4 to 20 carbon atoms and contains at least one saturated, unsaturated or aromatic heterocycle, or is a salt thereof.  
     
     
         28 . The electrolytic bath according to  claim 23 , wherein said organic compound is selected from the group consisting of propionaldehyde, butyraldehyde, isovaleraldehyde, valeraldehyde, capronaldehyde, hexaldehyde, 1-heptaldehyde, caprylic aldehyde, pelargonaldehyde, decanal, undecanal, laurylaldehyde, acrolein, crotonal, benzaldehyde, phenylacetaldehyde, cuminic aldehyde, cinnamaldehyde, anisic aldehyde, vanilline and phthalic aldehyde.  
     
     
         29 . The electrolytic bath according to  claim 23 , containing 1 to 100 g/L of gold.  
     
     
         30 . The electrolytic bath according to  claim 23 , containing at least one metal acting as inorganic brightener or as hardener.  
     
     
         31 . The electrolytic bath according to  claim 23 , containing at least one secondary metal selected from periods 4, 5 or 6 of Mendeleev's periodic classification of the elements, at a concentration of between 0.01 and 60 g/L.  
     
     
         32 . The electrolytic bath according to  claim 31 , wherein said secondary metal is selected from the group consisting of cobalt, nickel and iron.  
     
     
         33 . The electrolytic bath according to  claim 31 , wherein said secondary metal is introduced into said bath in the form of sulfate, carbonate, hydroxide, oxide, acetylacetonate, citrate, gluconate, sulphamate, or a mixture thereof.  
     
     
         34 . The electrolytic bath according to  claim 23 , containing an organic brightening agent.  
     
     
         35 . The electrolytic bath according to  claim 34 , containing 0.01 to 10 g/L 3-(3-pyridyl)acrylic acid or 3-(3-quinolyl) acrylic acid or a salt thereof.  
     
     
         36 . The electrolytic bath according to  claim 23 , containing at least 10 g/L of a conducting salt selected from the group consisting of citrates, phosphates, borates, sulfates and mixtures thereof.  
     
     
         37 . The electrolytic bath according to  claim 23 , containing a buffer for stabilizing pH.  
     
     
         38 . The electrolytic bath according to  claim 23 , further containing at least one wetting agent.  
     
     
         39 . The electrolytic bath according to  claim 23 , wherein gold is introduced in the form of cyanoaurate (I) or cyanoaurate (III).  
     
     
         40 . A method of electrodepositing gold or an alloy of gold, comprising electrolyzing an electrolytic bath as defined in  claim 23  with a current density of between 0.5 and 120 A/dm 2 .  
     
     
         41 . The method according to  claim 40 , wherein said electrolysis is carried out using insoluble anodes and cathodes made of a metallized substrate.  
     
     
         42 . A method for improving the speed of electrodeposition of gold or of one of its alloys and/or for reducing the contact resistance in a process of electrodeposition of gold or of one of its alloys from an aqueous electrolytic bath, wherein said bath comprises as auxiliary agent, an organic compound as defined in  claim 23 .  
     
     
         43 . The method according to  claim 42 , wherein said agent is used at a concentration of 0.3 to 3 mole per mole of gold contained in the bath.