Insufficienthole-fill/Exposedcopperonbottom-sideSMD
The most common defects that occur are insufficient solder, skips, a lack of hole-fill and grainy joints.
These defects are due to a variety of issues but with lead-free alloys and their reduced wetting potential,
coupled with higher pot temperatures, the flux selection will make the most difference in reducing their
occurrence. If the problem persists slowing down the conveyor speed to increase solder contact will
increase hole-fill.
The use of nitrogen at the solder pot area will reduce oxide creation but also increase solder wetting.
Nitrogen reduces oxide formation on board and components and with the reduced wetting behavior of
lead-free solders this can be an advantage. This is even more so if no-clean fluxes are used.