Electroless gold plating bath

Patent metadata

Field	Value
Publication number	US-11512394-B2
Application number	US-201816963522-A
Country	US
Kind code	B2
Filing date	Nov 19, 2018
Priority date	Jan 26, 2018
Publication date	Nov 29, 2022
Grant date	Nov 29, 2022

Abstract

The present invention concerns an electroless gold plating bath comprisinga) gold ions;b) sulfite ions;c) iodide ions;d) at least one phosphonate compound according to formula (1)whereineach X is independently an alkanediyl group;R1, R2, R3 and each R4 are independently alkanediyl groups;M is independently hydrogen, a metal atom or a cation forming radical;each n is a rational number and selected in accordance with the valency of the respective M; andb is an integer ranging from 1 to 10.The invention further is directed to the use of the bath and a method for depositing a gold layer on a surface of a substrate. The bath is particularly suitable in the manufacture of printed circuit boards, IC substrates, semiconducting devices, interposers made of glass and the like.

First claim

The invention claimed is:

1. An electroless gold plating bath, comprising
a) gold ions;
b) sulfite ions;
c) iodide ions; and
d) at least one phosphonate compound according to formula (1)

wherein
each X is an alkanediyl group;
R 1 , R 2 , R 3 and each R 4 are independently alkanediyl groups;
M is independently hydrogen, a metal atom or a cation forming radical;
each n is a rational number and selected in accordance with the valency of the respective M; and
b is an integer ranging from 1 to 10, and

wherein a molar ratio of gold ions to sulfite ions ranges from ⅓ to 1/20.

2. The electroless gold plating bath of claim 1 wherein the pH value of the electroless gold plating bath ranges from 5.5 to 8.5.

3. The electroless gold plating bath of claim 1 wherein the concentration of the sulfite ions ranges from 10 to 150 mmol/L.

4. The electroless gold plating bath of claim 1 wherein the concentration of the iodide ions ranges from 4 to 100 mmol/L.

5. The electroless gold plating bath of claim 1 wherein R 1 , R 2 , R 3 and each R 4 are independently C1-C6-alkanediyl groups.

6. The electroless gold plating bath of claim 1 wherein b ranges from 1 to 6.

7. The electroless gold plating bath of claim 1 wherein the electroless gold plating bath comprises at least one hydroxycarboxylic acid.

8. The electroless gold plating bath of claim 7 wherein the at least one hydroxycarboxylic acid is aliphatic.

9. The electroless gold plating bath of claim 7 wherein the at least one hydroxycarboxylic acid is a C1-C12-hydroxycarboxylic acid.

10. The electroless gold plating bath of claim 1 wherein the electroless gold plating bath is free of thiosulfate ions.

11. The electroless gold plating bath of claim 1 wherein the electroless gold plating bath is free of cyanide ions.

12. The electroless gold plating bath of claim 8 wherein the at least one hydroxycarboxylic acid is a C1-C12-hydroxycarboxylic acid.

13. The electroless gold plating bath of claim 1 wherein molar ratio of gold ions to sulfite ions ranges from ¼ to 1/16.

14. The electroless gold plating bath of claim 1 wherein the electroless gold plating bath is free of thiosulfate, is free of cyanide ions, and is free of thiourea.

15. The electroless gold plating bath of claim 1 wherein the electroless gold plating bath is free of thiourea.

Assignees

• Atotech Deutschland Gmbh

Inventors

• Lautan Donny
• Noethlich Christian
• Spreemann Robert
• Kraft Boris Alexander

Classifications

• C23C18/44 Primary

  using reducing agents · CPC title

• C08K3/105

  Compounds containing metals of Groups 1 to 3 or of Groups 11 to 13 of the Periodic Table · CPC title

• C08K3/30

  Sulfur-, selenium- or tellurium-containing compounds · CPC title

• C08K3/16

  Halogen-containing compounds · CPC title

• C23C18/42 Primary

  Coating with noble metals · CPC title