One of critical stage of surface assembly process is the thermal process that determines the phase changing of junction material (the solder paste or conductive adhesive). The equipment that does this treatment can transfer heat to assembly by convection, infrared radiation, or both. Each ones the dominant heat transfer inside the reflow oven, for some components (component’s manufacturer do it) in the last thermal zone (soldering zone), exist a maximum time and temperature to he not exceed. On the other hand, it exists a minimal product time-temperature to realize quality-soldering joints (from assembler point of view). To drive the process between these limits, some parameters of assembly must be previously evaluated. The assembly’s parameters tacking into account are the PCB thickness, the copper surface percentage, the vias density, the component density, the maximum thermal mass difference, and the light surface percentage. The goal of this paper is to emphasis the preliminary feedback that the assembler offers to improve quality designer purposes.