Water-soluble preflux, printed circuit board, and process for treating the surface of a metal in a printed circuit board

A water-soluble preflux comprising at least one compound selected from the group consisting of compounds represented by the following general formulae (1) and (3), at least one compound having the following general formula (2), and an iodine-based compound:

• where R1 is a straight-chain or branched-chain alkyl group having 1 to 7 carbon atoms, a halogen atom, an amino group, a di-lower alkylamino group, a hydroxy group, a lower alkoxy group, a cyano group, an acetyl group, a benzoyl group, a carbamoyl group, a formyl group, a carboxyl group, a lower alkoxycarbonyl group or a nitro group with the proviso that when R1 represents two or more groups, they may be different from or identical with each other, R2 is a straight-chain or branched-chain alkyl group, R3 is a phenyl group or an alkylphenyl group with the proviso that when R3 represents two or more groups, they may be different from or identical with each other, n is an integer of 0 to 4, and m is an integer of 0 to 3;
• where each of R4 and R5 is a straight-chain or branched-chain alkyl group having 1 to 7 carbon atoms, a halogen atom, an amino group, a di-lower alkylamino group, a hydroxy group, a lower alkoxy group, a cyano group, an acetyl group, a benzoyl group, a carbamoyl group, a formyl group, a carboxyl group, a lower alkoxycarbonyl group or a nitro group with the proviso that when each of R4 and R5 represents two or more groups, they may be different from or identical with each other, R5 may be a straight-chain or branched-chain alkyl group, a phenyl group, an alkylphenyl group or an phenylalkyl group with the proviso that when R5 represents two or more groups, they may be different from or identical with each other, n is an integer of 0 to 4, m is an integer of 0 to 10, and p is an integer of 0 to 4;
• and
• where R is a straight-chain or branched-chain alkyl group having 1 to 7 carbon atoms with the proviso that when R represents two or more groups, they may be different from or identical with each other, R6 is a straight-chain or branched-chain alkyl group having 1 to 7 carbon atoms with the proviso that when R6 represents two or more groups, they may be different from or identical with each other, n is an integer of 0 to 3, m is an integer of 0 to 4, p is an integer of 0 to 3, and q is an integer of 0 to 4.