Resin composition, and pre-preg, metal-clad laminate and printed circuit board prepared using the same

A resin composition, comprising:

• (A) a halogen-free epoxy resin;
• (B) a hardener;
• and
• (C) a phosphorus-containing phenolic resin of formula (I):
• in formula (I),
• n is 0, m is 0, and l is an integer of 1 to 10;
• and
• R1 and R2 are independently a residue of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), a residue of DOPO's derivative, a residue of amino triazine novolac (ATN) resin, or —O(CH2)3CH3, with the proviso that at least one of R1 and R2 is a residue of DOPO or a residue of DOPO's derivative,
• wherein the weight ratio of the hardener (B) to the phosphorus-containing phenolic resin (C) is from about 0.2:1 to about 0.9:1, and
• wherein based on 100 parts by weight of the halogen-free epoxy resin (A), the amount of the hardener (B) is about 9 parts by weight to about 52 parts by weight and the amount of the phosphorus-containing phenolic resin (C) is about 19 parts by weight to about 50 parts by weight.