GB/T 45013-2024 specifies the thermal fatigue test method for fine ceramic substrates used in power modules and electronic control units. The core principle involves simulating service environments through repeated thermal cycles between high and low temperatures, measuring the four-point bending strength and residual strength ratio of the substrates after thermal fatigue, and evaluating their durability. The standard defines the specifications, quantity requirements, and test procedures for rectangular sheet-shaped specimens, and is applicable to the performance testing and evaluation of substrates made from materials such as silicon nitride and alumina. The test requires the use of high-precision thermal cycling equipment, four-point bending strength testing instruments, and dimensional measurement tools such as micrometers and vernier calipers to ensure accurate test data, providing a unified technical basis for quality control and application selection of fine ceramic substrates.