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Solder Short
SOIC devices should be the limit for underside mounted components. Decreasing the pitch below 0.050" pitch will always increase defect levels or increase engineering time coaxing the process to solder 0.025" parts. The solder shorts are common on SOIC devices. If the short is in the middle of the row and the pad width is below 0.022" it is a process problem. Fluxing is the first area to examine, then look at adjustment to the contact time in the wave. Often changing the angle of the conveyor eliminates this defect. Unfortunately many wave soldering systems do not now allow this adjustment.