printed circuit boards of all types will possibly absorb moisture already during transportation and following storing, due to the hygroscopic property of its base material. This may lead to considerable problems at further processing, in particular with thermic processes.
Problem of moisture absorbtion
Recommended storage conditions and shelf life
Following storage conditions aid avoiding an additional humidity absorbtion of PCBs and preserving an optimal solderability.
Recommended storage conditions:
■storage temperature 18-22°C
■relative humidity 30-50 %
■no direct sunlight
■no contact with the skin
■clean ambient air
Acceptable shelf life of PCB surfaces:
Recommended tempering conditions
The processing of printed circuit boards demands a high degree of process stability.
Our printed circuit boards are already tempered during the manufacturing process, but neither delivery conditions (rain, temperature, etc.) nor storing conditions are optimal after dispatch.
For further processing, we therefore recommend a prior tempering of the printed circuit boards, especially after a longer storing period. This procedure raises the process stability considerably .
Accomplishment: Free-standing or horizontal in a circulating air oven.
Processing must take place directly after tempering (4 - 48 h), as the hygroscopic property of the base material persists.
General Recommendation
Printed circuit boards with immersion tin surface react with a faster growth of the intermetallic phase to a higher temperature (artifical aging). This can have a negative impact on the solderability.
Therefore, we recommend you to cooperate with an experienced, skilful assembly partner when processing immersion tin surfaces.
