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Printed circuit baking

Anti-delamination and breakage of components due to humidity.

At times the “delicacy” of the printed circuit board is underestimated, they are produced with a composite material called vetronite (FR-4) formed from a fabric of glass fibre woven into a flame-retardant epoxy resin. This material is particularly sensitive to humidity regardless of the packaging, because vetronite is hygroscopic.
During the soldering process, any moisture present in the PCB will be transformed into steam, which may cause external delamination defects of the solder mask, also called blistering.
In order to prevent such defects, as an adjunct to suitable packaging, drying (Baking) if appropriate of the printed circuit before entering production can also help; this treatment allows the complete elimination of moisture acquired by the printed circuit board.
This treatment is carried out before the use of the PCB 8-10 weeks after it has been produced and is carried out using a static oven, if possible with air circulation, overlapping no more than 10 boards one over the other and stacking them.
On the other hand, this process, if not controlled properly and if the time in the oven is extended longer than necessary, can seriously affect the solderability of the board, activating a process of premature ageing of the PCB.
Therefore, considering the printed circuit board as a perishable material is correct and it is normally advisable not to store it more than eight months unless otherwise indicated by the the manufacturer of the printed circuit board, even if these are packed under vacuum, usually airtight packages using nitrogen.
More generally, manufacturers of printed circuit boards suggest that storage takes place in closed environments suitable for storing this material and maintained at an ambient temperature of 20 degrees (range +/- 5 degrees) with maximum relative humidity (RH) 70%.