Prepreg, and metal-clad laminated board and wiring substrate obtained using same

A prepreg having a thermosetting resin composition or a semi-cured product of a thermosetting resin composition, and a fibrous base material, wherein

• the thermosetting resin composition contains
• (A) a thermosetting resin containing a modified polyphenylene ether compound and a crosslinking agent,
• (B) a first inorganic filler comprised of talc in which a molybdenum compound is present on at least a part of the surface, wherein the molybdenum compound is a compound containing at least one metal salt selected from zinc molybdate and calcium molybdate,
• and
• (C) a second inorganic filler comprised of spherical silica,
• the modified polyphenylene ether compound contains at least either
• a polyphenylene ether compound modified with methacrylic group or
• a polyphenylene ether compound modified with vinylbenzyl group,
• the crosslinking agent contains at least one selected from the group consisting of trialkenyl isocyanurate compound, polyfunctional methacrylate compound, polyfunctional acrylate compound, polyfunctional vinyl compounds, and vinyl benzyl compound,
• a content of (B) the first inorganic filler is 1 part by mass or more and 15 parts by mass or less, and a content of (C) the second inorganic filler is 50 parts by mass or more and 200 parts by mass or less, with respect to 100 parts by mass of (A) the thermosetting resin,
• the fibrous base material comprises a glass cloth containing quartz glass yarn,
• dielectric loss tangent at 10 GHz of a cured product of the prepreg is 0.002 or less, and
• the content of the modified polyphenylene ether compound is from 50 parts by mass to 90 parts by mass with respect to 100 parts by mass of a total of the modified polyphenylene ether compound and the crosslinking agent.