The vacuum will not be felt by the cavity of the component unless
the package is very porous. So no freezing will occur in this case
It will create a pressure difference and will facilitate the moisture
and air removal from inside the cavity due to the fact that pressures will
tend go to equilibrium. Packages absorb moist air, If the moisture froze, a
very small ball of ice would form On the other hand, temperature transmit
much faster and at 212 deg F plus, water molecules will boil and expand,
with the help of the air expansion, will cause popcorning.
Regards,
Ramon
> -----Original Message-----
> From: Dave Hillman [SMTP:[log in to unmask]]
> Sent: Tuesday, February 17, 2004 2:28 PM
> To: [log in to unmask]
> Subject: Re: [TN] Baking IC's to J-STD-033 that are not in a suitable
packaging
>
> Hi folks! Bev is correct - using a vacuum can actually impede moisture
> removal if the process is not correctly controlled. I have seen a very
neat
> demonstration where a container of water is subjected to a relatively fast
> vacuum cycle and you can observed the water surface convert to thick layer
> of ice! There are a number of investigations which shown that baking is a
> more efficient method of moisture removal but the downside is the
> degradation of the solderable surface finishes (which does not happen in
> the vacuum process).
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
>
>
> Bev Christian
> <[log in to unmask] To: [log in to unmask]
> ET> cc:
> Sent by: TechNet Subject: Re: [TN] Baking
IC's to J-STD-033 that are not in a suitable packaging
> <[log in to unmask]>
>
>
> 02/17/2004 09:37
> AM
> Please respond to
> "TechNet E-Mail
> Forum."; Please
> respond to Bev
> Christian
>
>
>
>
>
>
> Reuven,
> I have always wondered about that! Faster? And what about part
> reliability? In the cases where the elimination of water is not diffusion
> controlled, yes, it would be faster. However, if diffusion is the limiting
> step for the water coming to the surface of the component, then it does
not
> make any difference how fast you draw it off the surface. In fact, I
> wonder if you could evaporate it fast enough (at lower temperatures and
> high vacuum) that you could freeze the water, thus making the water act as
> its own plug and limiting you to the sublimation of the surface ice? And
> what about dropping the external pressure and thus decreasing the boiling
> point of the water so it flash evaporates even easier? Couldn't this then
> cause popcorning at, say 60C? I don't know, I'm asking.
> regards,
> Bev Christian
> Research in Motion
>
> -----Original Message-----
> From: Reuven ROKAH [mailto:[log in to unmask]]
> Sent: February 17, 2004 9:42 AM
> To: [log in to unmask]
> Subject: Re: [TN] Baking IC's to J-STD-033 that are not in a suitable
> packaging
>
>
> I recommend to be more careful with BGAs components (drying before
> production).
>
> Vacuum oven is recommended for low temp. packages. (faster).
>
>
> Best Regards
>
> ROKAH Reuven
>
>
>
>
> Kathy Kuhlow
> <[log in to unmask] To: [log in to unmask]
> OM> cc:
> Sent by: TechNet Subject: Re: [TN] Baking
> IC's to J-STD-033 that are not in a suitable packaging
> <[log in to unmask]
> >
>
>
> 17/02/2004 16:24
> Please respond
> to "TechNet
> E-Mail Forum.";
> Please respond>
> to Kathy Kuhlow
>
>
>
>
>
> We have a sealer, MBB bags, Labels, Desiccant, and indicator cards. When
> we kit to a work order we open the package count out what is needed. Then
> we repack both packages with the necessary items. The parts are put to
the
> kit and the inventory is returned. When any bag is cut open we look at
the
> indicator card and if the card is pink we bake them then. That way we
> don't have production waits for the rebaking process. If production
> returns moisture exposed parts we rebake prior to reinventory. Per 033 we
> look at this as described under 8.2.
>
> Kat
>
> >>> [log in to unmask] 02/17/04 03:25AM >>>
> Hi,
>
> What is the general working practice when say a class-3 device comes
> in vacuum shrinked wrapped with desicant and humidity indicator card
> but is in tubes/sticks packaging or even sometimes in reels.
>
> If the whole reel or pack of tubes are not all used up before the floor
> life
> expires and in theory the devices need to be re-processed @ 125 deg-C
> for 24-hours??
>
> I am wondering what most companies do regarding oven processing??
>
> Any knowledge of this would be interesting.
>
> Thanks,
> > Douglas I McCall
> > Printed Circuit Board Assembly Engineer,
> >
> > /// /// /// BOC EDWARDS
> H BOC Edwards, 15 Marshall Road, Eastbourne, East Sussex, England, BN22
> 9BA
> > * +44 (0)1323 501147
> * +44(0)1323 509824
> *+44 (0)7785 247 685
> > * mailto:[log in to unmask]
> >
> >
>
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