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