According to the present invention, there are provided a polycarbonate resin composition which comprises 40 to 92 wt % of an aromatic polycarbonate resin, 5 to 40 wt % of a styrene-based resin, 3 to 20 wt % of a phosphate-based flame retardant, and 0. The ring is locked axially on the hub between a pair of annular rims which project radially outwardly from the outer cylindrical surface of the ring and have been cold-deformed so as to engage two opposite surfaces of the hub. When the fan is started to operate, air convection is produced among the helical elongated members, forming helical whirls to increase contact and collision of the air with the helical elongated twisted fins, enhancing effect of heat dissipation. An intermediate layer conformal with the underlayer is provided. It also relates to novel particles suitable for use in such formulations. By providing the GaAs Substrate with a copper back-metal layer, the GaAs Substrate can be made thinner than 2 mils, thereby reducing heat dissipation problems and allowing the semiconductor die to be compatible with soft-solder technologies.