A system includes a heat sink module and a driving circuit module. The heat sink module includes stepped through-holes that each includes a cylindrical upper and lower portions connected by a ring-shaped surface. The bottom surface of the heat sink module includes grooves that respectively pass through the lower portions of respective sequences of the stepped through-holes. The driving circuit module includes conductive connectors and electrical driving surfaces that are disposed external to the heat sink module. Each conductive connector lies within a respective groove in the bottom surface of the heat sink module. The conductive connectors include internal connectors that each link at least two stepped through-holes in a respective sequence of stepped through-holes passed by a respective groove, and include external connectors that each link at least one stepped through-hole in the respective sequence of stepped through-holes to the electrical driving surfaces.