The document discusses options for printed circuit board base materials for thermally sensitive designs. It describes FR4, an inexpensive but thermally insulating material, and insulated metal substrates (IMS), which have high thermal conductivity but are expensive. The document introduces thermally conductive composite laminates as a third option that provides better thermal performance than FR4 at a lower cost than IMS. These composites fill the gap between the performance and price of FR4 and IMS for applications where heat dissipation is important.