Copper bath and methods of depositing a matt copper coating
View Patent ↗In the production of printed circuit boards it is required that organic protective coatings adhere tightly on the copper surfaces. Accordingly, matt layers of copper are to be preferred over lustrous coatings. The bath in accordance with the invention serves to deposit matt layers of copper and has the additional advantageous property that the layers may also be deposited with sufficient coating thickness in very narrow bore holes at average cathode current density. For this purpose the bath contains at least one polyglycerin compound selected from the group comprising poly(1,2,3-propantriol), poly(2,3-epoxy-1-propanol) and derivatives thereof.
1. An electrolytic copper plating bath for depositing a matt layer of copper comprising at least one copper salt, at least one acid, and at least one polyglycerin compound having at least one of the general formulae I, II or III:
wherein
n is an integer>1 and
R 1 , R 2 , R 3 are identical or different and are selected from the group consisting of H, alkyl, acyl, phenyl and benzyl; or
wherein
n is an integer>0,
m is an integer>0 and
R 1 , R 2 , R 3 , R 4 are identical or different and are selected from the group consisting of H, alkyl, acyl, phenyl and benzyl; or
wherein
n is an integer>0,
R 1 , R 2 , R 3 , R 4 are identical or different and are selected from the group consisting of H, alkyl, acyl, phenyl and benzyl.
2. The electrolytic copper plating bath of claim 1 , wherein the at least one polyglycerin compound is selected from the group consisting of poly(1,2,3 -propanetriol), poly(2,3-epoxy-1-propanol) and derivatives thereof.
3. The electrolytic copper plating bath of claim 1 , wherein the alkyl is linear or branched C 1 –C 18 alkyl and/or the acyl is R 5 —CO, wherein R 5 is linear or branched C 1 –C 18 alkyl, phenyl or benzyl.
4. The electrolytic copper plating bath of claim 1 , wherein the copper bath comprises a mixture A of at least two polyglycerin compounds, each polyglycerin compound having at least one of the general formulae I, II or III, said mixture A containing at least 90% by weight of a polyglycerin compound with n=4 and a maximum of 10% by weight of polyglycerin compounds with n=3 and/or 5, the sum of proportions of the polyglycerin compounds in mixture A amounting to 100% by weight of mixture A.
5. The electrolytic copper plating bath of claim 4 , wherein the concentration of mixture A of the polyglycerin compounds in the copper bath ranges from 0.3 g/l to 1.3 g/l.
6. The electrolytic copper plating bath of claim 1 , wherein the copper bath comprises a mixture B of at least two polyglycerin compounds, each polyglycerin compound having at least one of the general formulae I, II or III, said mixture B containing at least 40% by weight of a polyglycerin compound with n=4, a maximum of 50% by weight of polyglycerin compounds with n=2, 3 and/or 5 and a maximum of 20% by weight of polyglycerin compounds with n=6, 7, 8 and/or 9, the sum of proportions of the polyglycerin compounds in mixture B amounting to 100% by weight of mixture B.
7. The electrolytic copper plating bath of claim 6 , wherein the concentration of mixture B of the polyglycerin compounds in the copper bath ranges from 0.7 g/l to 2.6 g/l.
8. The electrolytic copper plating bath of claim 1 , wherein the copper bath comprises a mixture C of at least two polyglycerin compounds, each polyglycerin compound having at least one of the general formulae I, II or III, said mixture C containing from 30 to 35% by weight of a polyglycerin compound with n=4, from 50 to 60% by weight of polyglycerin compounds with n=2, 3 and/or 5 and 10 to 15% by weight of polyglycerin compounds with n≧6, the sum of proportions of the polyglycerin compounds in mixture C amounting to 100% by weight of mixture C.
9. The electrolytic copper plating bath of claim 8 , wherein the concentration of mixture C of the polyglycerin compounds in the copper bath ranges from 0.7 g/l to 2.6 g/l.
10. The electrolytic copper plating bath of claim 1 , wherein the polyglycerin compounds have a molecular weight ranging from 166 to 6000 g/mol.
11. A method of electrodepositing a matt layer of copper on the surface of a work piece, including the following method steps:
a. providing the work piece, at least one anode and an electrolytic copper plating bath;
b. contacting the surface of the work piece and the at least one anode, respectively, with the copper bath;
c. applying an electric voltage between the surface of the work piece and the at least one anode in such a manner that cathodic polarity is imposed upon the work piece relative to the at least one anode;
wherein the copper bath contains at least one polyglycerin compound having at least one of the general formulae I, II or III:
wherein
n is an integer>1 and
R 1 , R 2 , R 3 are identical or different and are selected from the group consisting of H, alkyl, acyl, phenyl and benzyl; or
wherein
n is an integer>0,
m is an integer>0 and
R 1 , R 2 , R 3 , R 4 are identical or different and are selected from the group consisting of H, alkyl, acyl, phenyl and benzyl; or
wherein
n is an integer>0,
R 1 , R 2 , R 3 , R 4 are identical or different and are selected from the group consisting of H, alkyl, acyl, phenyl and benzyl.
12. The method of claim 11 , wherein the alkyl is linear or branched C 1 –C 18 alkyl and/or the acyl is R 5 —CO, wherein R 5 is linear or branched C 1 –C 18 alkyl, phenyl or benzyl.
13. The method of claim 11 , wherein the copper bath contains a mixture A of at least two polyglycerin compounds, each polyglycerin compound having at least one of the general formulae I, II or III, said mixture A containing at least 90% by weight of a polyglycerin compound with n=4 and a maximum of 10% by weight of polyglycerin compounds with n=3 and/or 5, the sum of proportions of the polyglycerin compounds in mixture A amounting to 100% by weight of mixture A.
14. The method of claim 13 , wherein the concentration of mixture A of the polyglycerin compounds in the copper bath ranges from 0.3 g/l to 1.3 g/l.
15. The method of claim 11 , wherein the copper bath contains a mixture B of at least two polyglycerin compounds, each polyglycerin compound having at least one of the general formulae I, II or III, said mixture B containing at least 40% by weight of a polyglycerin compound with n=4, a maximum of 50% by weight of polyglycerin compounds with n=2, 3 and/or 5 and a maximum of 20% by weight of polyglycerin compounds with n=6, 7, 8 and/or 9, the sum of proportions of the polyglycerin compounds in mixture B amounting to 100% by weight of mixture B.
16. The method of claim 15 , wherein the concentration of mixture B of the polyglycerin compounds in the copper bath ranges from 0.7 g/l to 2.6 g/l.
17. The method of claim 11 , wherein the copper bath contains a mixture C of at least two polyglycerin compounds, each polyglycerin compound having at least one of the general formulae I, II or III, said mixture C containing from 30 to 35% by weight of a polyglycerin compound with n=4, from 50 to 60% by weight of polyglycerin compounds with n=2, 3, and/or 5 and 10 to 15% by weight of polyglycerin compounds with n≧6, the sum of proportions of the polyglycerin compounds in mixture C amounting to 100% by weight of mixture C.
18. The method of claim 17 , wherein the concentration of mixture C of the polyglycerin compounds in the copper bath ranges from 0.7 g/l to 2.6 g/l.
19. The method of claim 11 , wherein the polyglycerin compounds have a molecular weight ranging from 166 to 6000 g/mol.
20. The method of claim 11 , wherein the electric voltage is varied in such a manner that a pulsed current is made to flow between the work piece and the at least one anode.
21. The method of claim 11 , wherein the method further includes forming an organic coating on the matt layer of copper on the surface of the work piece.
22. The method of claim 21 , wherein the organic coating is a photoresist layer.
23. An electrolytic copper plating bath for depositing a matt layer of copper comprising at least one copper salt, at least one acid, and at least one polyglycerin compound selected from the group consisting of poly(1,2,3-propanetriol), poly(2,3-epoxy-1-propanol) and derivatives thereof.
24. The electrolytic copper plating bath of claim 23 , wherein the polyglycerin compounds have a molecular weight ranging from 166 to 6000 g/mol.
25. A method of electrodepositing a matt layer of copper on the surface of a work piece, including the following method steps:
a. providing the work piece, at least one anode and an electrolytic copper plating bath;
b. contacting the surface of the work piece and the at least one anode, respectively, with the copper bath;
c. applying an electric voltage between the surface of the work piece and the at least one anode in such a manner that cathodic polarity is imposed upon the work piece relative to the at least one anode;
wherein the copper bath contains at least one polyglycerin compound selected from the group consisting of poly(1,2,3-propanetriol), poly(2,3-epoxy-1propanol) and derivatives thereof.
26. The method of claim 25 , wherein the polyglycerin compounds have a molecular weight ranging from 166 to 6000 g/mol.
27. The method of claim 25 , wherein the electric voltage is varied in such a manner that a pulsed current is made to flow between the work piece and the at least one anode.
28. The method of claim 25 , wherein the method further includes forming an organic coating on the matt layer of copper on the surface of the work piece.
29. The method of claim 25 , wherein the organic coating is a photoresist layer.