Patent ID: 8491713

Claim:
An aqueous solution having a pH in the range of 1 to 5 for treating a tin or tin alloy surface comprising (a) at least one phosphorous compound or its salt represented by the following formulas I or II: wherein R1 is selected from the group consisting of H, OH, methyl, ethyl, n-propyl, isopropyl, n-hexyl, isohexyl, n-heptyl, isoheptyl, n-octly, isooctyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, isodecyl, n-dodecyl, isododecyl, R2 and R3 are the same or different and are selected independently from the group consisting of H, a counter ion, C 1 -C 20 -alkyl, substituted or unsubstituted, linear or branched, C 1 -C 6 -alkaryl, linear or branched, substituted or unsubstituted and aryl, substituted or unsubstituted and wherein n is an integer ranging from 2 to 10, R4 is F(CF 2 CF 2 ) z , z ranges from 1 to 7, x is 1 or 2, y is 1 or 2 and x+y is 3 and (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 counter ion, C 1 -C 20 -alkyl, substituted or unsubstituted, linear or branched, C 1 -C 6 -alkaryl, 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, linear or branched, substituted or unsubstituted and wherein R4 is selected from the group consisting of C 1 -C 12 -alkylene, linear or branched, substituted or unsubstituted, arylene 1,2-, 1,3- and 1,4-substituted, naphthylene, 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 formula 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, linear or branched.