sam mccorkel wrote:-
>We have a customer that wants us to begin using vaccuum sealed
>wrapping to ship their boards in. They want to reduce moisture absorbtion in
>the board.
>
>        It's been awhile, but I remember reading that this is a "No-No". I
>don't remember WHY but I think it had to do with trapped moisture.

Hi Sam,

I think a lot depends on the system used and how much air is in the bag
before the vacuum is pulled. As pressure reduces moisture in the air
will condense and remain in the pack at a high relative humidity. A
better system would apply external pressure to expel the air before
final vacuum sealing but the remaining spaces in the holes would still
have a high relative humidity due to the low pressure.

Vacuum packing might be suitable for longer term storage provided the
panels are baked after unwrapping. This only needs to for about 30 mins
at 100 C (212 F).

Regards
Paul Gould
[log in to unmask]
Teknacron Circuits Ltd
Isle of Wight,UK

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