A resin sheet is made using a resin composition containing a thermosetting component (A). The thermosetting component (A) contains a maleimide resin. A thermal diffusion rate of the thermally cured resin sheet is 1.0 × 10.sup.-6 m.sup.2/s or more. The resin sheet has a thickness in a range from 5 .Math.m to 120 .Math.m .

A resin composition includes 20 parts by weight to 45 parts by weight of a phosphorus-containing bismaleimide and 100 parts by weight of a thermosetting resin, wherein the phosphorus-containing bismaleimide has a structure of Formula (I); the thermosetting resin is selected from a vinyl-containing polyphenylene ether resin, a maleimide resin, a polyolefin resin, a prepolymer of maleimide resin, and a combination thereof. The resin composition may be used to make a prepreg, a resin film, a laminate or a printed circuit board, and at least one of the following properties can be improved, including flame retardancy, outgassing properties, arc resistance, copper foil peeling strength, X-axis coefficient of thermal expansion, glass transition temperature and water absorption rate.

##STR00001##

A resin composition includes 20 parts by weight to 45 parts by weight of a phosphorus-containing bismaleimide and 100 parts by weight of a thermosetting resin, wherein the phosphorus-containing bismaleimide has a structure of Formula (I); the thermosetting resin is selected from a vinyl-containing polyphenylene ether resin, a maleimide resin, a polyolefin resin, a prepolymer of maleimide resin, and a combination thereof. The resin composition may be used to make a prepreg, a resin film, a laminate or a printed circuit board, and at least one of the following properties can be improved, including flame retardancy, outgassing properties, arc resistance, copper foil peeling strength, X-axis coefficient of thermal expansion, glass transition temperature and water absorption rate.

##STR00001##

A film containing: a propenyl group-containing resin (A) including, at an end of a molecule, a constituent unit represented by the following formula (1); a radical polymerizable resin or compound (B) other than the propenyl group-containing resin (A); and a curing accelerator (C), wherein the radical polymerizable resin or compound (B) includes at least one selected from the group consisting of a maleimide group and a citraconimide group. In the formula (1), —* represents a bonding hand.

A film containing: a propenyl group-containing resin (A) including, at an end of a molecule, a constituent unit represented by the following formula (1); a radical polymerizable resin or compound (B) other than the propenyl group-containing resin (A); and a curing accelerator (C), wherein the radical polymerizable resin or compound (B) includes at least one selected from the group consisting of a maleimide group and a citraconimide group. In the formula (1), —* represents a bonding hand.

Provided is a resin composition having high thermal resistance and low dielectric properties, as well as a cured product, a prepreg, a metal foil-clad laminate, a resin sheet, and a printed wiring board. The resin composition contains a compound (A) represented by Formula (M1) and a cyanate ester compound (B) containing two or more aromatic moieties per molecule, the aromatic moieties being replaced by at least one cyanato group: where in Formula (M1), A is a four- to six-membered alicyclic group:

##STR00001##

Provided is a resin composition having high thermal resistance and low dielectric properties, as well as a cured product, a prepreg, a metal foil-clad laminate, a resin sheet, and a printed wiring board. The resin composition contains a compound (A) represented by Formula (M1) and a cyanate ester compound (B) containing two or more aromatic moieties per molecule, the aromatic moieties being replaced by at least one cyanato group: where in Formula (M1), A is a four- to six-membered alicyclic group:

##STR00001##

Curable polyimides and compositions thereof with very good dielectric properties are provided. Prepregs of these compositions laminated with copper foil to prepare copper clad laminates having Tg>150 C and Df<0.0025 are also provided.

Curable polyimides and compositions thereof with very good dielectric properties are provided. Prepregs of these compositions laminated with copper foil to prepare copper clad laminates having Tg>150 C and Df<0.0025 are also provided.

Provided is a resin composition which has good solubility and photocurability, further has good alkaline-developability when containing a photo initiator and a compound containing one or more carboxyl groups, and in addition, is capable of providing a resin sheet having suppressed tackiness; and a resin sheet, multilayer printed wiring board, and semiconductor device using the same. The resin composition of the present invention contains a particular bismaleimide compound (A), and at least two maleimide compounds (B) selected from the group consisting of six kinds of particular compounds which are different from this bismaleimide compound (A).