MEMS solder self-assembly technique can assemble the quasi-three-dimensional microstructures to the final three-dimensional devices using the surface tension of the molten solder. A model based on the minimum surface energy principle has been developed. Experimental studies are conducted to verify the model. It is shown that the final rotating angle matches well with the predicted angle, and the error is less than ±3°. By analyzing the impact of factors on the solder self-assembly process, the parameter K and the pad aspect ratio P_k were determined as the dominant factors. Finally, the influencing regularities of the dominant factors affecting the equilibrium angles are obtained with further studies.