Abstract: A pre-preg substrate, having a low dielectric constant and containing a substantially uniformly distributed hollow-glass-microsphere filler, and method for making the same. The pre-preg substrate is treated with impregnation and lamination techniques to form a laminate with a low dielectric constant, and good mechanical and electrical properties, suitable as a base material for surface mounted devices in high performance circuits. Improved pre-pregs for making high performance circuit boards and for making surface mounted integrated circuits. Improved high performance circuit boards for making surface mounted integrated circuits.

Abstract: A carboxylated latex is added to an aqueous slurry of fibers to remove metal ions contained in solution. The water is removed to form a felt. The demetallized water removed during felt formation is recycled in a closed process water system. The carboxylated latex is formed by polymerizing an unsaturated carboxylic acid on a substantially surfactant free styrene-diene polymer latex.