Capillary Wetting Current
Capillary wetting flow is the flow of molten solder within a narrow solder gap, driven by surface tensions. It determines the cycle time in industry.
Physico-chemical mechanism of action
Capillary wetting flow occurs due to the surface tension between the molten solder and the metallic workpieces. This tension creates a pressure that pulls the solder towards the smallest diameter (the solder gap).
Metallurgical relevance & risks when welding
A too low capillary wetting flow can lead to long cycle times and insufficient wetting, resulting in missing connections or pores in the solder joint. Conversely, a too high flow can lead to excessive wetting and too much melting of the workpieces.
Workshop practice & instructions
To optimize the capillary wetting flow, control the surface tension of the solder. This can be achieved by choosing the right solder composition and temperature. A typical cycle time for industrial brazing processes is about 1 to 2 seconds, depending on the specific materials and the solder gap.