Drying flexible and flex-rigid circuit boards

Drying before soldering is a must!

Flexible and rigid-flex circuit boards with polyimide are hygroscopic, i.e. they absorb moisture from the air even under normal room conditions. A dried polyimide laminate e.g. reaches its moisture saturation point after only a few hours of exposure. During the soldering process, the absorbed moisture can vaporise explosively, resulting in damage such as delaminating, formation of bubbles, cracks, etc. The original packaging is not fire protected.

The drying process must be qualified by the manufacturer; the drying recommendations only serve as guidelines based on experience. See here our extensive drying recommendations!

In order to facilitate and optimize the drying process, we have created a document that you can use for your planning.

A detailed application note „Physics of moisture & process of drying printed circuit boards“ can be found here: