Chapter 4. Physicochemical Foundations of Electric Mounting Soldering

To ensure the formation of high-quality solder joints, it is imperative to engage in surface preparation of the materials being joined, activate both the materials and solder, eliminate oxide films in the contact zone, facilitate interaction at the interfacial boundary, and induce crystallization of the liquid metal layer. This chapter delves into the processes involved in removing surface oxide films from solderable surfaces and discusses the pertinent equipment employed. Additionally, it highlights the potential efficacy of ultrasonic methods in oxide film removal through the introduction of elastic mechanical vibrations into the molten solder. Mathematical expressions are derived to elucidate the dynamics at the solder-surface interface, during the capillary penetration of solder into gaps and the diffusion process. The formation of a soldered joint with a specific structure results from the physicochemical interaction between the solder and the base metal. This joint typically encompasses a melting zone and diffusion zone at the solder and the base metal interface. The ultimate structure and composition of the solder joint depend on the nature of the interacting metals, their chemical affinity, and the soldering conditions, including time and temperature.