Electroless plating solution, method for electroless plating using the same and method for manufacturing circuit board

An electroless plating solution at least containing a water-soluble metal salt, a reducing agent and a chelating agent, and also containing a leveler composed of at least one of sulfur-based organic compounds represented by the following formulas (I) to (V):

• R1—(S)n—R2 (n≧3) (I)
• R1-L1-(S)n—R2 (n≧1) (II)
• R1-L1-(S)n-L2-R2 (n≧1) (III)
• R1—(S)n-L3 (n≧1) (IV)
• R1-L1-(S)n-L4 (n≧1) (V)
• wherein, in the above formulas (I) to (V), R1, R2 each independently denotes an aliphatic cyclic group or an aromatic cyclic group containing optional numbers of carbon, oxygen, phosphorus, sulfur and nitrogen atoms, provided that at least one optional substituent of at least one species may be linked to the aliphatic cyclic or aromatic cyclic group;
• wherein in the above formulas (II), (III) and (V), L1, L2 each independently denotes one of a straight or a branched alkyl, alkyl amino, alkylene or alkoxy chain;
• wherein in the above formula (IV), L3 denotes one of alkylene, amino, alkyl amino, alkylene amino, hydroxyl, alkyl hydroxyl, alkylene hydroxyl, carboxyl, alkyl carboxyl, alkylene carboxyl, alkyl amino carboxyl, alkylene amino carboxyl, nitro, alkylnitro, nitrile, alkylnitrile, amide, alkylamide, carbonyl, alkyl carbonyl, sulfonic acid, alkylsulfonic acid, phosphonic acid, alkylphosphonic acid, sulfanyl, sulfinyl and thiocarbonyl groups;
• and
• wherein in the above formula (V), L4 denotes one of an alkyl, alkylene, amino, alkyl amino, alkylene amino, hydroxyl, alkyl hydroxyl, alkylene hydroxyl, carboxyl, alkyl carboxyl, alkylene carboxyl, alkyl amino carboxyl, alkylene amino carboxyl, nitro, alkylnitro, nitrile, alkylnitrile, amide, alkylamide, carbonyl, alkyl carbonyl, sulfonic acid, alkylsulfonic acid, phosphonic acid, alkylphosphonic acid, sulfanyl, sulfinyl and thiocarbonyl groups.