An IC package is disclosed that comprises a core region disposed between upper and lower build-up layer regions. In one embodiment, the core region comprises a low modulus material. In an alternative embodiment the core region comprises a medium modulus material. In an alternative embodiment, the core material is selected based upon considerations such as it modulus, its coefficient of thermal expansion, and/or the resulting total accumulated strain. In an alternative embodiment, boundaries with respect to the softness of the core material are established be considering the reflective density in opposing conductive build-up layers above and below the core region.