Method of making a flexible substrate with a filler material

Abstract

A method of adding a thermally conductive, electrically nonconductive filler to a flexible substrate such as a polyimide core. The substrate may be used, for example, as a part of a polyimide core for a tape or an interposer in a BGA or similar integrated circuit package. The resulting substrate has a higher thermal conductivity as compared to conventional substrates without fillers, thereby increasing the thermal dissipation through the substrate and enabling the device to cool more efficiently. The filler also reduces the coefficient of thermal expansion of the substrate to more closely match the die and reduce stresses. Furthermore, the filler increases the rigidity of the substrate, thereby enabling the device to be handled and carried more easily, for example, without a metal frame carrier.