The supply of molten solder – providing solder for wetting and filling the gaps. This is a function of:
the solderability of both surfaces
design (pad to component ratio and fillet control)
wave dynamic
As indicated, both parts of the process depend on wave dynamics or, more plainly, on the shape of the solder being pumped, its fluidity, flow rate and turbulence. There are a large number of wave designs but most are variations on the same technology (Figure 7).