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February 2012

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TechNet E-Mail Forum <[log in to unmask]>, Bev Christian <[log in to unmask]>
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Fri, 24 Feb 2012 08:09:24 -0600
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TechNet E-Mail Forum <[log in to unmask]>, "Stadem, Richard D." <[log in to unmask]>
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"Stadem, Richard D." <[log in to unmask]>
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I knew you would answer that one, Bev.
My question, is Siliporite/molecular sieves the same thing as desiccant pads?

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Friday, February 24, 2012 5:37 AM
To: [log in to unmask]
Subject: Re: [TN] Siliporite molecular sieve

Cedric,
I had to look up was Siliporite was!  Molecular Sieves.  So the only reason
you would put molecular sieves in an oven is to regenerate them.  I would
PRESUME - to drive off the water they have collected from whatever process
you used them in.  Molecular sieves can be used for many different things,
but you did use the word "drying".  Wikipedia says "Temperatures typically
used to regenerate water-adsorbed molecular sieves range from 130 °C to 250
°C.[2]"  The reference being: "Sudhir Joshi, James R. Fair (November 1988).
"Adsorptive drying of toluene". Ind. Eng. Chem. Res. 27 (11): 2078-2085".
So I can see a few potential problems here. If the temperature of your oven
is anywhere above the low end of the range needed to dry out the molecular
sieves, you are going to grow intermetallic up through thin HASL or
immersion tin, potentially drive off organics from OSP or immersion silver
and/or oxidize any of the last three coatings.  On top of that if there are
enough molecular sieves, they are heavily laiden with water and there is
poor air flow in the oven you are going to be subjecting your boards to a
sauna.  You have essentially put them in a humidity chamber.  Not a good
idea.

Bev
RIM

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Cedric ORAIN
Sent: Friday, February 24, 2012 5:21 AM
To: [log in to unmask]
Subject: [TN] Siliporite molecular sieve

Hello all,

It is said by some "old school" colleagues that drying siliporite in the
same oven than pcb could lead to solderability issue ? Is some of you have
knowledge about what could happen having siliporite and PCB in the same oven
?

Best regards,

Cedric ORAIN
www.inovelec-groupe.com



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