Aqueous indium or indium alloy plating bath and process for deposition of indium or an indium alloy

1. A process for deposition of indium or an indium alloy comprising the steps of:

i. providing a substrate ( 100 ) having at least one metal or metal alloy surface;

ii. contacting the at least one surface of said substrate ( 100 ) with an aqueous indium or indium alloy plating bath comprising:

a source of indium ions,

an acid,

a source of halide ions,

a surfactant according to formula (I)

wherein A is selected from branched or unbranched C 10 -C 15 -alkyl;

B is selected from the group consisting of hydrogen and alkyl;

m is an integer ranging from 5 to 25;

each R is independently from each other selected from hydrogen and methyl; and

a dihydroxybenzene derivative according to formula (II)

wherein each X is independently selected from fluorine, chlorine, bromine, iodine, alkoxy, and nitro;

n is an integer ranging from 1 to 4,

wherein, when the aqueous indium or indium alloy plating bath is an indium alloy plating bath, an alloying reducible metal is selected from the group consisting of aluminum, bismuth, copper, gold, lead, nickel, silver, tin, tungsten and zinc;

and thereby depositing an indium layer or indium alloy layer on at least a portion of the at least one surface, and

wherein

in step ii. the indium or indium alloy layer is a first indium or indium alloy layer ( 101 ),

in step ii. a composed phase ( 102 ) is formed, made of the metal or metal alloy of said surface ( 100 a ) and at least a part of the first indium or indium alloy layer ( 101 ),

wherein the process further comprises the steps:

iii. removing partially or wholly the part of the first indium or indium alloy layer which has not been converted into the composed phase ( 103 ); and

iv. depositing a second indium or indium alloy layer ( 104 ) on at least a portion of the surface obtained in step iii ( 102 a ).

2. The process according to claim 1 , wherein depositing the indium layer or indium alloy layer in step ii. is carried out by electrolytic deposition.

3. The process according to claim 2 , wherein the electrolytic deposition is a potentiostatic deposition process.

4. The process according claim 1 , wherein depositing the second indium layer or indium alloy layer ( 104 ) in step iv. is carried out by electrolytic deposition and the electrolytic deposition is a potentiostatic deposition process.

5. The process according claim 1 , wherein step iii. is carried out by a electrolytic stripping process and the electrolytic stripping process is a potentiostatic stripping process.

6. The process according to claim 1 , wherein each R is selected from hydrogen and methyl such that hydrogen and methyl are present in a ratio of hydrogen/methyl of 10/1 to 100/1.

7. The process according to claim 1 , wherein R is hydrogen.

8. The process according to claim 1 , wherein the acid is selected from one or more of alkane sulfonic acid and sulfuric acid.

9. The process according to claim 1 , wherein the surfactant has a value for hydrophilic-lipophilic balance (HLB value, determined according to method of Griffin) ranging from 13.0-18.0.

10. The process according to claim 1 , wherein the dihydroxybenzene derivative is 4-chloro resorcinol, 5-methoxy resorcinol, chloro hydroquinone, 4-bromo resorcinol, 2-nitro resorcinol or 4-chloro catechol.

11. The process according to claim 1 , wherein the aqueous indium or indium alloy plating bath has a pH of −1 to 4.

12. The process according to claim 1 , wherein the aqueous indium or indium alloy plating bath further comprises a source of alkali metal cations and/or a source of alkaline earth metal cations.