The next question is: how do you verify that you are successful?
Ahne.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: 15 April, 2013 08:31
To: [log in to unmask]
Subject: Re: [TN] Pakeout and PCB Separators
Inge,
Did you want a serious response or just a Causerie? :-)
If you attempt to remove all the oxygen, every single atom, then only your
success rate will hit ZERO.
Actually, now that I think about it, bare metal in a vacuum chamber might
just serve as a "Getter" like the coatings inside old vacuum tubes. So I do
wonder how effective a vacuum chamber might be in reducing oxidation at
elevated temperatures. It might help but I don't know.
Bob
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
Sent: Sunday, April 14, 2013 2:43 PM
To: [log in to unmask]
Subject: Re: [TN] Pakeout and PCB Separators
Oxidation...Oxygeg.question for Bob: Remember our little discussion on
'zero' . What I ask now has no practical application. I have had the thought
before when I used ultrahigh vacuum (exp -12)..Now to question: Is it
possible to remove all oxygen molecules in a volum made of xxxxx. I mean
zero molecules, not one single molecule. Or is there a place in Universe
where a Oxygen atom is unthinkable?
Inge
On 10 April 2013 16:54, Robert Kondner <[log in to unmask]> wrote:
> I will agree about oxidation but not faster drying. I mean the vapor
> pressure of water is already quite low at room temperature. I think
> drying time for a material with absorbed vapor is fixed by diffusion
> rates and distance. And temperature is a bit driver of diffusion rate.
> Is air pressure even in the equation?
>
> Bob K.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
> Sent: Tuesday, April 09, 2013 2:12 PM
> To: [log in to unmask]
> Subject: Re: [TN] Pakeout and PCB Separators
>
> Baking in Vacuum oven = less pads oxidation and faster drying
>
>
> On Tue, Apr 9, 2013 at 9:00 PM, Glidden, Kevin
> <[log in to unmask]>wrote:
>
> > Someone in Technet not long ago posted up an excellent little write
> > up from Gordon Davy about water vapor and drying. I've attached it
> > to Phil and Bob.
> >
> > It contends vacuum ovens do nothing to increase drying rate.
> >
> > Drying is a function of temperature and delta between concentration
> > of water in the middle versus at the surface.
> >
> > I presume, like any drying, the greater the surface area exposed the
> > faster the drying. I would place the PCBs (as much as possible)
> > directly on racks or in card holders (on edge).
> >
> > -----Original Message-----
> > From: Nutting, Phil [mailto:[log in to unmask]]
> > Sent: Tuesday, April 09, 2013 1:01 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Pakeout and PCB Separators
> >
> > Robert,
> >
> > How about placing them in a vacuum chamber. That would release all
> > the moisture and definitely if you could add a little heat. I would
> > envision separating the boards with a mesh and spacer to allow the
> > moisture to fully escape. Placing a paper towel between layers
> > might not let all the moisture escape.
> >
> > But then this is just my opinion.
> >
> > Phil Nutting
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
> > Sent: Tuesday, April 09, 2013 12:54 PM
> > To: [log in to unmask]
> > Subject: [TN] Pakeout and PCB Separators
> >
> > Hi,
> >
> >
> >
> > Does anyone know if separators of some type between PCBs can reduce
> > bake out time?
> >
> >
> >
> > If I have a stack of PCBs, and I place something like paper towels
> > between PCBs, can the bake out time be reduced? I would imagine the
> > diffusion rates of moisture in the paper towel material would be
> > much higher than in solid PCB laminate. But, that is just a guess.
> > Could be
> perfect hog wash.
> >
> >
> >
> > My problem is not with PCBs but with 30 mil sheets of plastic that
> > feed a thermoforming process. I am using PETG but I still see small
> > bubbles in the material after forming. I tried a short bake out, and
> > it helps, but I cannot heat very high as the 30 mil plastic sheets
> > will easily deform. I need to lay them flat, heat gently, and still
> > try to removed moisture. I was wondering what the best way to
> > separate sheets and allow drying might be.
> >
> >
> >
> > Any Ideas?
> >
> >
> >
> > Thanks,
> >
> > Bob K.
> >
> >
> >
> >
> >
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