The current development of soldering materials focuses on the properties of the solder itself, while the reliability of the joints formed after soldering is evaluated to a lesser extent. It is essential to understand the relationship between the structure and the strength of the solder joint obtained. This article shows that the properties of the material used for soldering only to a certain extent largely translate into the mechanical properties of the joint. The aim of this article is to emphasize the importance of the problem of the selection of the chemical composition of the solder with the simultaneous selection of the parameters of the soldering process, including the width of the solder gap for the selected strength properties of the connection. The purpose of this article is to emphasize that the selection of a chemical composition solder with a simultaneous selection of parameters of the soldering process, including the dimensions of the gaps of the soldered materials, are affected properties of the soldered joint. In this article, the main importance was focused on the chemical composition of a tin-based solder. The influence was analyzed, and the most favorable content of elements, such as Al and Cu, which create intermetallic phases, strengthening the soldered joint, was determined. The properties of the newly developed solder joint for alternator applications due to the specified conditions of the soldering process, including the width of the solder gap permissible for alternators, ensured the correct connections, the strength properties of which differed despite the use of the same soldering material and substrate material, as well as the soldering time and tip temperature. This article presents a change in the cracking model of a solder joint made using a newly developed material due to the width of the permissible solder gap in the production process of alternators.