Twisting / Warping
The elevated temperatures experienced by the printed circuit boards during the soldering process may cause boards to twist or to warp. Twisting or warping may change, in the wave soldering or selective soldering process, the distance of the solder surface to the nozzle, which will give rise to changes in the soldering parameters. In the reflow process, problems may arise through change in the printing or in the pick-and-place process for the second side. For this reason, it should be the goal to maintain, throughout all processes, the planarity, the flatness of the boards. Causes for twisting or warping are manifold, they could lie in the construction of the printed circuit board, in the distribution of internal copper, or in the depth of scoring for break-aways.