This thesis develops a model based approach to support the decarbonization of a semiconductor assembly line by coupling discrete event simulation with stage level energy and emissions accounting. The case study is a surface mount technology (SMT) line at Hapro Electronics (Line 5, Jaren, Norway). The model, built in AnyLogic, represents PCB assembly flow (preparation, solder paste printing and SPI, pick and place, reflow heating/cooling, AOI, storage) and is parameterized with a mix of sensor readings and equipment data sheets to estimate per stage energy, queueing, throughput, and CO₂ outcomes. Baseline analysis shows a clear separation of levers: the reflow (heating) stage is the dominant energy hotspot and primary driver of the line’s carbon footprint, whereas the pick and place (PnP) station governs flow throughput, cycle time, and work in process (WIP).