Considerable efforts are presently being made to improve miniaturization of optical devices and to achieve at the same time submicron assembly precision. Several groups are working on concepts based on passive alignment techniques (ex. integrated waveguide structures Si-bench technology) or on the more flexible automated surface mounting techniques based on in-situ alignment procedures during assembly. A detailed knowledge on the thermal behaviour of the miniaturized components becomes inevitable for achieving the desired assembly precision and stability during operation. Here, we report on the thermal behaviour and heat dissipation characteristics of the standardized optical mounts used in the three dimensional miniaturized optical surface mounted device (TRIMO-SMD) technology