Hi Garcia,
You didn't mention the most important variable: the process technology, the
vapor pressure (300 to 650 psi) of Lead free is more than double than Leaded
process at the reflow peak temp.
the MAMC for Leaded process should be 0.20% and for Lead Free 0.17%. (ref.
Werner Engelmaier PCB FAB Notes).
Reuven

On Fri, Oct 21, 2011 at 8:31 PM, Garcia, Rigo (GSFC-300.0)[MANTECH SRS
TECHNOLOGIES] <[log in to unmask]> wrote:

> Hi everybody,
>
> Does anybody know how do we determine the Maximum Acceptable Moisture
> Content (MAMC) for a board?
>
> I understand that IPC-1601 states that for most designs a MAMC between 0.1%
> and 0.5% of moisture weight to resin weight is adequate. However, it does
> not describe the basis to establish the range. I can think of many variables
> that can affect this number like minimum pitch, voltage across, component
> clearance, whether the board gets conformal coating or not, etc. I would
> like to know if anybody knows of a safe method to determine the MAMC for a
> given board.
>
> Paul... I can already see your "it depends" coming... :)!
>
> Thanks for the help!
>
> Rigo Garcia
>
> Sr. Quality Assurance Engineer
> Workmanship Standards, Code 300
> NASA, Goddard Space Flight Center
> Greenbelt, MD  20771
> Phone. (301) 286-6129
> Fax.       (301) 286-6576
>
>
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