Solution and process for increasing the solderability and corrosion resistance of metal or metal alloy surface

1. An aqueous solution for treating a metal surface comprising

(a) at least one phosphorous compound or its salt represented by the followings formulas

wherein R1, R2 and R3 are the same or different and are selected independently from the group consisting of H, a suitable counter ion, C 1 -C 20 -alkyl, which may be substituted or unsubstituted, linear or branched, C 1 -C 6 -alkaryl, which may be linear or branched, substituted or unsubstituted, and aryl, which may be substituted or unsubstituted and wherein n is an integer ranging from 1 to 15

(b) at least one solderability-enhancing compound or its salt represented by the following formula

wherein m, n, o and p are integers ranging from 0 to 200 and are the same or different and m+n+o+p is at least 2

wherein R1 and R7 are the same or different and are selected independently from the group consisting of H, a suitable counter ion, C 1 -C 20 -alkyl, which may be substituted or unsubstituted, linear or branched, C 1 -C 6 -alkaryl, which may be linear or branched, allyl, aryl, sulfate, phosphate, halide and sulfonate and wherein each of the R2, R3, R5 and R6 groups may be the same or different and are selected independently from the group consisting of H and C 1 -C 6 -alkyl, which may be linear or branched, substituted or unsubstituted and wherein R4 is selected from the group consisting of C 1 -C 12 -alkylene, which may be linear or branched, substituted or unsubstituted, arylene which may be 1,2-, 1,3- and 1,4-substituted, naphthylene, which may be 1,3-, 1,4-1,5-1,6- and 1,8-substituted, higher annulated arylene, cylcloalkylene, —O—(CH 2 (CH 2 ) n OR1, wherein R1 has the meaning defined above, and moieties represented by the following formulas

wherein the substitution independently is 1,2-, 1,3- or 1,4 for each ring and wherein q and r are the same or different and range independently from 0 to 10 and R8 and R9 are selected independently from the group consisting of H and C 1 -C 6 -alkyl,which may be linear or branched;

wherein the at least one phosohorous compund (a) represented by the formulas I.-VI. is in an amount of 0.0001 to 0.05 mol/l.

2. An aqueous solution according to claim 1 , wherein R1, R2 and R3 of the phosphorous compounds I.-VI. are selected independently from the group consisting of H or a suitable counter ion, methyl, ethyl, n-propyl, isopropyl, n-hexyl, isohexyl, n-heptyl, isoheptyl, n-octyl, isooctyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, isoundecyl, n-dodecyl, and isododecyl.

3. An aqueous solution according to claim 1 , wherein R1 of the phosphorous compounds I.-VI. is selected from the group consisting of n-propyl, isopropyl, n-hexyl, isohexyl, n-heptyl, isoheptyl, n-octyl, isooctyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, isoundecyl, n-dodecyl, and isododecyl and wherein R2 and R3 are H.

4. An aqueous solution according to claim 1 , wherein R1 and R7 of the solderability-enhancing compound VII. are selected independently from the group consisting of H, methyl, sodium, potassium, halide, sulfate, phosphate and sulfonate.

5. An aqueous solution according to claim 1 , wherein R2, R3, R5 and R6 of the solderability-enhancing compound VII. are selected independently from the group consisting of H, methyl, ethyl, n-propyl and isopropyl.

6. An aqueous solution according to claim 1 , wherein R4 of the solderability-enhancing compound VII. is selected from the group represented by the following formulas

and wherein R8 and R9 are selected from the group consisting of H, methyl, ethyl, n-propyl and isopropyl.

7. An aqueous solution according to claim 1 , wherein the solderability-enhancing compound VII. is selected from the group consisting of the following formulas

wherein n=1-20,

wherein n=1-20 and

wherein n=1-20.

8. An aqueous solution according to claim 1 , wherein the at least one solderability-enhancing compound (b) represented by the formula VII. is used in an amount of 0.0001 to 0.1 mol/l.

9. An aqueous solution according to claim 1 , wherein the pH value is between 2 and 5.

10. An aqueous solution according to claim 1 , wherein a buffer system selected from the group consisting of formic acid/formiate, tartaric acid/tartrate, citric acid/citrate, acetic acid/acetate and oxalic acid/oxalate is contained.

11. An aqueous solution according to claim 1 or 2 , wherein the counter ion is sodium or potassium.

12. A process for increasing the solderability and corrosion resistance of a substrate having a metal surface wherein the surface is treated with an aqueous solution according to claim 1 .

13. The process according to claim 12 , wherein the metal surface is a tin or tin alloy surface.

14. The process according to claim 13 , wherein the tin alloy surface is selected from the group consisting of SnPb, SnCu, SnBi, SnAg and SnAgCu surfaces.

15. The process according to claim 12 further comprising reflowing the tin or tin alloy surface of the substrate prior or after treatment with the aqueous solution.

16. Substrate having a tin or tin alloy surface treated with the aqueous solution according to claim 1 .

17. Substrate according to claim 16 , wherein the substrate is selected from the group consisting of a tin plate, tin wire, lead frame, connector and printed circuit board.

18. An aqueous solution for treating a metal surface comprising

(a) at least one phosphorous compound or its salt represented by the followings formulas

wherein R1, R2 and R3 are the same or different and are selected independently from the group consisting of H, a suitable counter ion, C 1 -C 20 -alkyl, which may be substituted or unsubstituted, linear or branched, C 1 -C 6 -alkaryl, which may be linear or branched, substituted or unsubstituted, and aryl, which may be substituted or unsubstituted and wherein n is an integer ranging from 1 to 15

(b) at least one solderability-enhancing compound or its salt represented by the following formula

wherein m, n, o and p are integers ranging from 0 to 200 and are the same or different and m+n+o+p is at least 2

wherein R1 and R7 are the same or different and are selected independently from the group consisting of H, a suitable counter ion, C 1 -C 20 -alkyl, which may be substituted or unsubstituted, linear or branched, C 1 -C 6 -alkaryl, which may be linear or branched, allyl, aryl, sulfate, phosphate, halide and sulfonate and wherein each of the R2, R3, R5 and R6 groups may be the same or different and are selected independently from the group consisting of H and C 1 -C 6 -alkyl, which may be linear or branched, substituted or unsubstituted and wherein R4 is selected from the group consisting of C 1 -C 12 -alkylene, which may be linear or branched, substituted or unsubstituted, arylene which may be 1,2-, 1,3- and 1,4-substituted, naphthylene, which may be 1,3-, 1,4-1,5-1,6- and 1,8-substituted, higher annulated arylene, cylcloalkylene, —O—(CH 2 (CH 2 ) n OR1, wherein R1 has the meaning defined above, and moieties represented by the following formulas

wherein the substitution independently is 1,2-, 1,3- or 1,4 for each ring and wherein q and r are the same or different and range independently from 0 to 10 and R8 and R9 are selected independently from the group consisting of H and C 1 -C 6 -alkyl, which may be linear or branched;

wherein the at least one solderability-enhancing compound (b) represented by the formula VII. is used in an amount of 0.0001 to 0.1 mol/l.

19. An aqueous solution according to claim 18 , wherein R1, R2 and R3 of the phosphorous compounds I.-VI. are selected independently from the group consisting of H or a suitable counter ion, methyl, ethyl, n-propyl, isopropyl, n-hexyl, isohexyl, n-heptyl, isoheptyl, n-octly, isooctyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, isoundecyl, n-dodecyl, and isododecyl.

20. An aqueous solution according to claim 18 , wherein R1 of the phosphorous compounds I.-VI. is selected from the group consisting of n-propyl, isopropyl, n-hexyl, isohexyl, n-heptyl, isoheptyl, n-octly, isooctyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, isoundecyl, n-dodecyl, and isododecyl and wherein R2 and R3 are H.

21. An aqueous solution according to claim 18 , wherein R1 and R7 of the solderability-enhancing compound VII. are selected independently from the group consisting of H, methyl, sodium, potassium, halide, sulfate, phosphate and sulfonate.

22. An aqueous solution according to claim 18 , wherein R2, R3, R5 and R6 of the solderability-enhancing compound VII. are selected independently from the group consisting of H, methyl, ethyl, n-propyl and isopropyl.

23. An aqueous solution according to claim 18 , wherein R4 of the solderability-enhancing compound VII. is selected from the group represented by the following formulas

and wherein R8 and R9 are selected from the group consisting of H, methyl, ethyl, n-propyl and isopropyl.

24. An aqueous solution according to claim 18 , wherein the solderability-enhancing compound VII. is selected from the group consisting of the following formulas

wherein n=1-20,

wherein n=1-20 and

wherein n=1-20.

25. An aqueous solution according to claim 18 , wherein the at least one phosphorous compound (a) represented by the formulas I.-VI. is used in an amount of 0.0001 to 0.05 mol/l.

26. An aqueous solution according to claim 18 , wherein the pH value is between 2 and 5.

27. An aqueous solution according to claim 18 , wherein a buffer system selected from the group consisting of formic acid/formiate, tartaric acid/tartrate, citric acid/citrate, acetic acid/acetate and oxalic acid/oxalate is contained.

28. An aqueous solution according to claim 18 or 19 , wherein the counter ion is sodium or potassium.

29. A process for increasing the solderability and corrosion resistance of a substrate having a metal surface wherein the surface is treated with an aqueous solution according to claim 18 .

30. The process according to claim 29 , wherein the metal surface is a tin or tin alloy surface.

31. The process according to claim 30 , wherein the tin alloy surface is selected from the group consisting of SnPb, SnCu, SnBi, SnAg and SnAgCu surfaces.

32. The process according to claim 29 further comprising reflowing the tin or tin alloy surface of the substrate prior or after treatment with the aqueous solution.

33. Substrate having a tin or tin alloy surface treated with the aqueous solution according to claim 18 .

34. Substrate according to claim 33 , wherein the substrate is selected from the group consisting of a tin plate, tin wire, lead frame, connector and printed circuit board.