Wednesday, 3 December 2014

reflow - Vacuum dessication of MSL components?


The standard method of removing moisture from MSL-sensitive SMD components prior to reflow is to bake in an oven for 12 hours or more. Without baking, there is a possibility of popcorning, as the absorbed moisture expands rapidly (as steam) leading to high pressure and mechanical failure. Ranier Dudek explains popcorning here and ISU.edu hosts a failure-mode paper showing actual cases here.


But ovens require a lot of power and time to remove this moisture. Could an alternative be vacuum dessication?


Vacuum pump and dessicating chamber


A vacuum pump would still boil the moisture away, but without the large pressures of steam, correct? And once evacuated, the vessel could sit unpowered for days if needed, saving energy.


Is this viable for SMD components? I see where vacuum storage and packaging is utilized for SMD, but not vacuum dessication itself.





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