<p>In this study, a AlN heater-based simple creep-rupture tester was developed for durability and quality assessment of solder joints for high temperature. It is designed to apply normal and thermal stress simultaneously in the direction of gravity and adjust its magnitude accordingly. This test device allows the observation of creep-rupture changes in various solder joints under thermal–mechanical combined stress. Using the device as case study, creep-rupture quality assessment was conducted on 97.5Pb2.5Sn solder joints—a high-temperature melting solder exceeding 300 °C. As the thermal stress reached 230 °C and the normal loads increased to 4.9, 9.8, and 14.7 N, the failure time decreased according to a power-law distribution. Application of normal stress in the range of 1.5–3.0 N/mm² was found to be suitable as a test method for the device under test. FEA results, using a refined hyperbolic sine creep model, showed that maximum shear stress, strain, and strain energy density were strongly influenced by load magnitude, with higher loads causing significant creep deformation and earlier rupture. The von Mises equivalent stress correlated linearly with rupture time on a logarithmic scale, validating experimental trends. Creep quality assessment of Silver (Ag) paste demonstrated superior creep durability compared to traditional Pb-rich solders, with the ability to withstand extended thermal stress at 230 °C under normal loads of 4.9 N and 9.8 N. The results of this study confirm the effectiveness of the developed creep tester utilising both normal and thermal stress for creep quality assessment of solder joints.</p>