A circuitized substrate including a composite layer comprising a first dielectric sub-layer comprised of a halogen-free resin and fibers dispersed therein and a second dielectric sub-layer without fibers but also including a halogen-free resin with inorganic particulates therein. A method of making such a substrate is also provided, as is a multilayered assembly including one or more such circuitized substrates, possibly in combination with other substrates. An information handling system designed for having one or more such circuitized substrates is also provided.