A very long time ago, (so I can only remember the outcome not the detail) I
was on the periphery of a study in this area, made over months. The outcome
was that heat sealing was better but partially for reasons not associated
with moisture barrier effectiveness.
The conclusion was heat sealing was better because, it was surmised, it
avoided the interface of silicone adhesive bond (from the tape) and a simple
fold. It was also a more consistent process. Heat sealing also gave a more
tamper proof control in the overall. An unforeseen side benefit: it gave the
customer auditors a rosy glow.
Vacuum sealing was not really beneficial although evacuation of the bags was
thought good, again partially as a tamper proofer. Desiccants were effective
specifically those with an indicator, but for genuine long term storage a
dry nitrogen cabinet was best. I'm not sure there is anything profound in
these comments.
I also recall we have had this conversation before [several times], but the
thread I am really thinking of was probably about 9-10 years back, this
included actual data. It was memorable to me because I recall thinking this
would have been really useful back in... I checked my own archive to see if
I kept it, but I haven't. Possibly a trawl through the TechNet archive would
reveal something.
Regards
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Tuesday, October 16, 2012 12:51 AM
To: [log in to unmask]
Subject: Re: [TN] board baking - thread continuation
Bob,
I don't know how they compare, mainly because you don't say how big of a
surface area and the length of the incomplete seal and also the fact that I
can't do the math anyways. :(
But unless one is talking about real moisture barrier bags that are totally
sealed, then you are just talking about "short term" protection anyways. ALL
plastics let water diffuse. Non-porous aluminum doesn't, unless it corrodes
through.
Bev
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Monday, October 15, 2012 11:35 AM
To: [log in to unmask]
Subject: Re: [TN] board baking - thread continuation
Hi,
According to content on some sites simple taping might be OK and heat seal
not required.
I wonder how moisture diffusion through an incomplete tape seal and a bend
compares to bag surface diffusion.
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Glen Herzog
Sent: Monday, October 15, 2012 12:10 AM
To: [log in to unmask]
Subject: Re: [TN] board baking - thread continuation
Joyce Koo recommended a dry box. I agree that that is recommended,
especially for short term use such as you've used some of the components and
you will use the rest in a few days to a few weeks. However, if you need
longer term storage I recommend purchasing moisture barrier bags, desiccant
and moisture indicator cards. They're relatively inexpensive. You would
need a heat sealer ($200-$300 and simple to use) I would not worry about
vacuuming the bag, it's probably not worth the effort. The formula for how
much desiccant to use depends on what desiccant is used. For example you
might take look at:
http://texastechnologies.com/moisture-control/desiccant/silica-gel/packaged/
sorb-it-silica-gel-unit-size.htm
for one example. I have no investment in that company, it's just a
reference to an example.
Good luck
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
|
