In this chapter, we comprehensively discuss the primary varieties of solders and fluxes utilized in the fabrication of electrical connections within electronic modules. Particular emphasis is placed on the challenges associated with the use of lead-free soldering materials. A potential resolution to these challenges involves the modification of solder compositions, potentially transitioning towards nanoscale architectures. A promising avenue of exploration lies in the utilization of water-based fluxes and flux gels. Water-based fluxes containing surfactant additives offer notable advantages, particularly in their application via spray mechanisms. They exhibit robust stability and mitigate thermal shock occurrences during soldering operations. Furthermore, we delve into the characteristics of solder pastes employed in the surface mounting of electronic modules, elucidating their application methodologies, operational considerations, and optimal storage practices. Additionally, we provide a comprehensive overview of conductive adhesives utilized in the formation of contact connections. The chapter also examines the primary types of mounting microwires employed in ultrasonic and thermosonic microwelding processes, alongside outlining the role of protective liquids in the cleaning of connections.
