A method of preparing a rigid polyurethane foam having improved thermal conductivity, and a composition for such rigid polyurethane foam is provided. Additionally, a mezzanine board has a plurality of mezzanine board connector sites each adapted to receive a connector and configured to provide access to a number of mezzanine traces interconnecting the LBCSs. The semiconductor element includes a solder bump formed on a first electrode pad through a first low melting point solder layer. This abstract is submitted with the understanding that it will not be used to interpret or limit the scope. The instant abstract is neither intended to define the invention disclosed in this specification nor intended to limit the scope of the invention in any way.