## 1 Introduction  
The evolution of lead-free solder alloys, particularly in the context of electronic manufacturing, represents a significant shift in material science and engineering. While the use of soldering for mechanical and electrical connections has a long history, recent advancements have been driven by the need for environmentally friendly and high-performance alternatives to traditional tin-lead (Sn-Pb) solders. Soldering electronic components together using'soft soldering', which involves much lower temperatures, is a much more recent development. Early soft soldering employed pure tin. Alloys were created over time to solve challenges such as thermal cycling, shock tolerance, electron migration, and whisker formation in tin-based alloys [1]. Although lead could play this role in most soldering applications, the elimination of lead from devices and the implementation of new standards for more fine-pitched parts necessitated the development of new solder alloys. To be considered a viable alternative to Sn-Pb solders, lead-free candidates must offer qualities and functionality comparable to or greater than those of eutectic or close eutectic Sn-Pb solders. The presence of Pb in solders improves the overall efficiency of the Sn-Pb solder. In addition to carrying electricity, solder joints provide mechanical support for electrical devices. As a result, the mechanical qualities of solder alloys are critical in the production of long-lasting products. Tensile characteristics and creep are particularly important for evaluating the mechanical properties of solders and have consequently been widely researched [2]. SAC is an abbreviation for the alloy SnAgCu (tin, silver, and copper). SAC alloys are the most widely utilised alloys in the electronics industry. SAC305, a lead-free grade alloy, is made up of 96.5% tin, 3% silver, and 0.5% copper. Its 3% silver component ensures optimum wetting qualities as well as balanced thermal fatigue, solder link power, and mechanical stress resistance [3]. Solder pastes are made up of a metal alloy powder (about 90% by weight) and a cream-like organic chemical component (approximately 10% by weight). 'Flux', the cream of organic components, is usually a trade secret or patent-protected [4]. This study aims to delve deeper into the mechanical behaviour of Pb-free solder alloys, specifically their response to different strain rates and constant stresses. A model considering both elastic and plastic deformation along with creep behaviour is being developed to accurately represent the stress-strain characteristics of these alloys [5; 6]. The mechanical characteristics of lead-free solders, particularly SAC305, are highly dependent on parameters such as temperature and strain rate. This reliance is caused by the high homologous temperature of these solder alloys, which makes comparing results across research difficult. Such disparities are caused by a lack of consistent testing circumstances, which includes differences in specimen preparation processes and strain rates. Despite these difficulties, a broad spectrum of mechanical characteristics has been determined. The elastic modulus of SAC alloys, including SAC305, normally ranges from 30 to 54 GPa, with the majority of values falling between 40 and 50 GPa. In terms of tensile parameters, the Sn-3.9 Ag-0.5 Cu variation has an elastic modulus of 50.3 GPa, an ultimate tensile strength (UTS) of 54 MPa, and a yield strength (YS) of 36.2 MPa. Variations in these values are observed between research, which can be attributed to the various testing procedures used. As a result, these stated data must be evaluated with caution, taking into account the high heterogeneity due to the various production technologies and conditions [7]. SACX0807 (Alpha SACX Plus 0807) is a low-silver lead-free alloy intended to give soldering and reliability characteristics equal to those of higher-silver SAC305. Tensile properties and microstructure are compared with SAC305 in [8].