STORAGE GUIDELINES FOR BARE (UNPOPULATED) PCB’S

The shelf life of pcb’s are dependent on the storage conditions as well as the surface finish. The laminate material is sensitive to moisture absorption and the surface finish of the pcb’s can be affected by contamination and oxidation.

Flex and flex-rigid pcb’s are more prone to moisture absorption due to the hygroscopic nature of the polyimide material used as part of the flex circuit.

The PCBs / panels will ideally need to be stored as follows:

The PCBs / panels will ideally need to be stored as follows:

• Use vacuum-sealed packaging (original packaging is ideal), if the package is damaged then it will need to be resealed to offer optimal protection.
• Package to contain a desiccant (drying agent) for moisture absorption, this will assist in removing and displacing any moisture present inside the sealed package.

If properly stored, the shelf life of a pcb, depending on the surface finish can be as follows:

The above table serves as a guideline only.

As an example of the above table, an Immersion Gold (ENIG) finish pcb can last up to 12 months, this period is determined from the date of manufacture of the pcb’s (date code which indicates week and year of manufacture).

It would be very difficult to determine a shelf life once the original vacuum-sealed packaging has been opened, many factors would contribute to the integrity of the pcb’s. The main concerns would be moisture and contamination/oxidation of the surface finish (solderability). It would be safer to re-vacuum seal the remaining pcb’s/panels as soon as possible after the original packaging has been opened.