8 Reasons for Selective Wave Soldering Solder Bridging

Excessive length of component pins prevents individual desoldering when departing from the solder wave, or prolonged immersion of pins in the solder wave leads to burnt flux, reducing solder flowability and causing solder bridging between adjacent points.
Large soldering angles decrease the probability of points departing the wave in a co-planar manner, thus reducing the risk of bridging.
Excessive component density, improper pad design, or incorrect soldering direction for socket and IC-type components.
Inadequate preheating temperature results in incomplete activation of flux, leading to insufficient PCB temperature and reduced wetting and flowability of liquid solder, resulting in solder bridging between adjacent tracks.
Unclean PCB surface affects the flowability of liquid solder on its surface, causing solder to easily clog between solder points, forming solder bridges.
Poor flux quality fails to clean the PCB, resulting in decreased wetting of solder on the copper foil surface, leading to poor wetting effects.
Excessive immersion depth of PCB in solder wave causes complete decomposition or poor flow of flux, preventing solder points from completing the desoldering process in good condition.
PCB deformation causes inconsistent pressure wave depths, leading to poor solder flow and easy formation of solder bridges.