Hi team - as Bev discussed, a vacuum bake process can work against you if
the process parameters are not correct. I have actually created ice using
the wrong parameter set. A well run temperature bake process is just as
effective and considerably less costly for removing board moisture. And
what most folks mess up is the board storage after bake out. As many folks
have detailed, proper bagging or use of drying cabinets is critical to not
having the bake out be a wasted effort.

Dave

On Tue, Sep 11, 2018 at 7:40 PM, Bev Christian <[log in to unmask]>
wrote:

> Wayne,
> I believe that Dave Hillman has rightly said that vacuum can be
> counterproductive if there is enough water (and not enough heat) that
> pulling water out by vacuum lowers the temperature of the water/vapor
> interface enough that the water freezes lowering the removal rate
> substantially. Note my use of a few weasel words.
>
> Bev
>
> -----Original Message-----
> From: TechNet <[log in to unmask]> On Behalf Of Robert Kondner
> Sent: Tuesday, September 11, 2018 7:12 PM
> To: [log in to unmask]
> Subject: Re: [TN] PCBs in dry chambers
>
> Wayne,
>
>  Thanks but I had zero luck searching through the archives, probably pilot
> error.
>
>  But I looked into IPC1601 and it did say "Air Flow is Critical". I wonder
> how that jives in a vacuum? I also saw some references to the need for air
> flow to heat by convention, that makes sense.
>
> Backout at 125C can degrade finishes so I would like to dry out PCBs in a
> dry box. I have seen info from McDry showing rates of moisture removal.
> Seems the times are about 10 - 30 hours at 30C. This data is for ICs, I am
> curious what might apply to PCBs. I would much rather dry at 30C for a long
> period of time than 125C. I am wondering if anyone knows of any data.
>
> Thanks,
> Bob K.
>
> -----Original Message-----
> From: TechNet <[log in to unmask]> On Behalf Of Wayne Showers
> Sent: Tuesday, September 11, 2018 6:30 PM
> To: [log in to unmask]
> Subject: Re: [TN] PCBs in dry chambers
>
> http://listserv.ipc.org/scripts/wa.exe?A0=TechNet this will also show the
> monthly archive tabs
>