A hybrid-filled, electrically insulating composition includes a resinous matrix comprising 56 to 65 volume percent of the total composition and a particulate dispersed phase comprising essentially the balance of the total composition. The dispersed phase includes a first ceramic component such as AlN, BN, or BeO and a second ceramic component such as MgO, Al.sub.2O.sub.3, SiO.sub.2, a polycrystalline alumino-silicate, and/or a metal. The dispersed phase makes up more than 50 volume percent of the first component. The molding composition has a thermal conductivity of at least 3.5 W/mK.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 The United States Government has rights in this invention pursuant to contract no. DE-AC05-000R22725 between the United States Department of Energy and UT-Battelle, LLC.