## 1 Introduction
The corrosion behaviour of SAC305 and SACX0807 under application conditions was correlated with the microstructure of the alloy and the electrochemical behaviour in [9; 10]. The creep behaviour of SACX0807 has not yet been reported. This is an important gap in the field that should be covered by this work (at room temperature). With a focus on SAC alloys such as SAC305 or SACX0807, it is necessary to investigate the Strain Rate Sensitivity (SRS) of the material. The peculiar microstructure of this alloy, which includes Sn, Ag3 Sn, and Cu6 Sn5, has a substantial impact on its mechanical behaviour at varied strain rates. In particular, SAC305 exhibits a decrease in SRS as the temperature and strain rate increase, which is an important element in determining the mechanical stability of solder connections in electronic devices [11]. This discovery is especially important in operational settings involving dynamic mechanical loads. Understanding these correlations is critical for forecasting solder performance and guaranteeing electronic assembly durability [12]. The fatigue life of SAC305 under different wave loading situations, as investigated in publications [13; 14; 15], gives important insights into the solder's behaviour. By including both plastic and creep strain components, they considerably improve our knowledge of SAC305 fatigue behaviour. Another critical consideration is the effect of ageing on the fatigue life of SAC305 [16]. The lower mechanical fatigue life due to age, notably in SAC305, shows the importance of a thorough examination of stress relaxation and low cycle fatigue features. A recent study [5] emphasises the importance of the constitutive viscoplastic model for SAC305 and provides an in-depth look at the ratcheting behaviour of SAC305 under cyclic loading, highlighting its lower time-dependent deformation compared to Sn-37 Pb. This difference is due to the distinct microstructural and mechanical characteristics of SAC305, which emphasises the exceptional capacity of the material to carry cyclic loads. This is critical for the dependability of mechanically stressed electronic systems. Some authors of the paper developed a special experimental technique based on the Digital Image Correlation (DIC) method, which enables the acceleration of the testing regarding the necessity of material model calibration, as well as the obtaining of deformation characteristics under different modes of loading [17; 18; 19; 20; 21]. It is based on measuring the history of strain on the curved part of the standard specimen for mechanical testing. Therefore, it brings extra data to the measurement by the extensometer, leading to a more efficient way of testing stress-strain behaviour. Using the newly developed DIC technique, it is possible to efficiently obtain the cyclic stress-strain curve [18] or several ratcheting curves at lower loading levels [17]. This time, to the knowledge of the authors, the developed DIC technique is first applied to the creep of solder alloys. The first applications to the experimental analysis of creep of additively prepared composites and metals are reported in [19; 20; 21]. For numerical simulations of the SAC305 material, the Anand material model is often used, see [22]. The Anand material model was designed for hot working metals [23] and can capture the effect of temperature and strain rate. Anand model is described by using nine parameters. Tensile tests and creep tests are frequently solved separately [24]. In the literature, different parameter values can be found for similar or even the same materials, see [25]. The parameter value is usually determined by the least squares method as a non-linear regression from compression [23], tensile or creep tests [24]. Article [25] presents the parameter values for a material labelled (Sn95.5 Ag3.8 Cu0.7) from three different papers. The parameter values differ very significantly, for example, parameter \(\mathrm{A}=\left(15.773\div 1.63\times 10^{6}\right)\). The problem is also solved in [26].