Abstract: To address the issue that the solder layer is prone to failure due to creep deformation, the creep behaviors of three types of solders, namely Sn96.5Ag3.5, Sn96.5Ag3.0Cu0.5, and Sn95Sb5, were systematically studied based on tensile creep tests. Firstly, based on the results of tensile creep tests, the Garofalo constitutive models for the three solders were established, and the creep properties of the three solders were compared. Then, the parameters of the Garofalo constitutive models were verified, and the sensitivities of the parameters were analyzed. Finally, the SEM fracture morphologies of the three solders after tensile creep tests were observed, and their creep behaviors and fracture mechanisms were analyzed. The results indicate that Sn95Sb5 solder is more suitable for long-term high-temperature working conditions than Sn96.5Ag3.5 and Sn96.5Ag3.0Cu0.5 solders. In addition, the fitting accuracies of the Garofalo constitutive models for the three solders are relatively high, and the order of the sensitivities of the model parameters from high to low is parameter α—parameter Q—parameter n—parameter A. By comparing the fracture morphologies, it is found that the increase in temperature and stress load causes the fracture mechanism to gradually change from ductile fracture to brittle fracture. Under high-temperature and high-stress conditions, the fracture surfaces of Sn96.5Ag3.5 and Sn96.5Ag3.0Cu0.5 solders exhibit more grains, and they are more prone to brittle fracture or intergranular fracture; the fracture surface of Sn95Sb5 solder exhibits more dimples, indicating that its fracture mechanism is mainly ductile fracture.