Abstract: To address the local critical responses of solder joints in spaceborne ceramic leadless chip carrier (CLCC) devices under multi-condition service environments, including vacuum thermal cycling, random vibration and shock loading, a finite element model of the CLCC device–solder joint–PCB assembly was established. The response characteristics of the solder joints under different service conditions were analyzed. Solder climbing height, stand-off height, pad dimensions, PCB thickness and device placement were selected as design variables. A multi-condition finite element dataset was constructed using Latin hypercube sampling. Candidate surrogate models were evaluated, and the Gaussian process regression (GPR) model was selected to rapidly predict the thermal cycling PEEQ, random vibration Mises stress and shock Mises stress. Based on the selected surrogate model, the NSGA-II multi-objective optimization algorithm was used to obtain structural parameter combinations considering multi-condition reliability, and the optimization results were verified by finite element recalculation. The results show that the optimized design reduces the thermal cycling PEEQ, random vibration Mises stress and shock Mises stress by 48.31%, 35.74% and 13.92%, respectively. The proposed method can effectively reduce the critical responses of CLCC solder joints under multi-condition service environments and provide a reference for reliability-oriented design of electronic packaging solder joints.