Silicon-containing curable composition, cured product of the silicon-containing curable composition and lead frame substrate formed of the silicon-containing curable composition

A silicon-containing curable composition comprising:

• as component (A), 100 parts by mass of a silicon-containing polymer having a weight average molecular weight of 3,000 to 100,000, which is obtainable by hydrolysis-condensation of an organosilane mixture comprising 5 to 50 mol % of one or more kind of (a) an organosilane represented by the following formula (1-1), 0 to 50 mol % of one or more kind of (b) an organosilane represented by the following formula (1-2), 0 to 40 mol % of one or more kind of (c) an organosilane represented by the following formula (1-3) and 0 to 50 mol % of one or more kind of (d) an organosilane represented by the following formula (1-4), wherein the total of the organosilane (b) and organosilane (c) is 5 to 60 mol %;
• as component (B), 0 to 200 parts by mass of a prepolymer comprising two or more Si—H groups in one molecule, which is obtainable by a hydrosilylation reaction of one or more kind selected from (α) a cyclic siloxane compound represented by the following formula (2) and one or more kind selected from (β) a compound represented by the following formula (3) or (3′);
• as component (C), 0 to 30 parts by mass of a cyclic siloxane compound comprising two or more carbon-carbon double bonds having reactivity with Si—H groups in one molecule;
• as component (D), 0.0001 to 10 parts by mass of an organic peroxide and 0 to 1.0 parts by mass of a metal catalyst, and
• as component (E), 10 to 1,500 parts by mass of a filler
• R1SiX3 (1-1)
• R2SiX3 (1-2)
• R3R4SiX2 (1-3)
• R5SiX3 (1-4)
• wherein R′ is an alkenyl group having 2 to 6 carbon atoms, R2 is an alkyl group having 1 to 6 carbon atoms, and R3 and R4 are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms or a phenyl group optionally substituted by an alkyl group having 1 to 6 carbon atoms, wherein at least one of R2, R3 and R4 is a methyl group, R5 is a phenyl group optionally substituted by an alkyl group having 1 to 6 carbon atoms, and X is a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms or a halogen atom,
• wherein in the formula (2), R6, R7 and R8 each independently represents an alkyl group having 1 to 6 carbon atoms or a phenyl group optionally substituted by an alkyl group having 1 to 6 carbon atoms, wherein R6s of a number of f may be the same or different and R's of a number of g and R8s of a number of g each may also be the same or different, f represents a number of 2 to 10, g represents a number of 0 to 8, and f+g≧2,
• wherein in the formula (3), n represents 1 or 2.