General information about sagging of printed circuit boards during the soldering process

For a well controlled soldering operation it is important that the boards are kept as flat as possible. Sagging of the printed circuit board will lead to different soldering conditions for the individual joints. Also flooding of solder can occur or components may jump out of their holes if the protruded leads touch the nozzle.
Sagging happens almost always due to a combination of effects which are also each a reason for board sagging themselves.
The formulas given in this sheet are worked out in more detail on separate information sheets for each subject.