US Patent 8187696 Circuit materials, circuits laminates, and method of manufacture thereof

A circuit substrate laminate, comprising a conductive metal layer; and a dielectric composite material having a dielectric constant of less than about 3.5 and a dissipation factor of less than about 0.006, wherein the dielectric composite material comprises: a polymer resin; and about 10 to about 70 volume percent of cenospheres having a ferric oxide content of less than or equal to 3 weight percent.