The role of flux in wave soldering for PCBAprocessing plant

Wave soldering flux is usedin electronic assembly PCBA processing plant is the main electronic auxiliarymaterials, the quality of its good or bad directly determines the reliabilityof subsequent products, the following is a brief description of the role offlux in wave soldering.

① Remove the rust film onthe surface of the soldered metal. The surface of the soldered metal is notsoluble in any solution, but these rust and some materials to chemicalreaction, the generation of compounds that can be soluble in liquid flux, youcan remove the rust film, to purify the surface of the soldered metal. Thischemical reaction can be made flux dissolved in flux or flux solvent of anothercompound. Fluxes belonging to the first chemical reaction is mainly representedby rosin flux, as an example of the second chemical reaction is certain gaseswith reducing properties. For example, oxygen reduces oxides on metal surfacesat high temperatures, generating water and restoring a pure metal surface.

②Preventing secondaryoxidation of the metal being soldered during the heating process. Wave welding,with the rise in temperature, the metal surface re-oxidation phenomenon willintensify, so flux must provide protection for the metal surface has been purified,wrapped metal, so that it is isolated from the air, to achieve the role of theheating process in the welding to prevent the secondary oxidation of the weldedmetal.

③ Reduce the surfacetension of the liquid solder. Fluxes in the welding process can affect theenergy balance of the surface by promoting the diffusion of solder, reducingthe surface tension of the liquid solder and reducing the contact angle.

④ Heat transfer. The headto be welded are generally a number of gaps, in the welding process, the air inthese gaps play a role in the partition, which leads to poor heat transfer. Ifthese gaps are filled with flux, the transfer of heat can be accelerated andheat balance can be achieved.

⑤ Promote the diffusion ofliquid solder. After preheated flux and wave solder contact, the activityincreases sharply, the viscosity drops sharply, and a second diffusion isformed on the surface of the soldered metal, and quickly spread out on thesurface of the soldered metal. Flux second diffusion process formed by thediffusion force, attached to the liquid solder, thus dragging the diffusionprocess of the liquid metal.