Richard S,
Thanks for the reference, but it merely wetted my appetite. haha.
This information offers a data point, but 'maximum' is misleading. The
values given in the slash sheets are for the 24 hour point, what about
at 25 hours, or at equilibrium? When does equilibrium occur?
I am beginning to see why this data isn't readily available. With
variables of temperature and RH, creating a chart for just one material
would be an effort, and that doesn't even consider how varying circuitry
and material layers would affect the diffusion rate for a PWB.
Ben
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, May 29, 2007 11:11 AM
To: [log in to unmask]
Subject: Re: [TN] PWB Moisture Diffusion Rates
Ben, Richard K,
Maximum moisture absorption levels are part of the requirements for the
PWB Base Materials and are listed in the individual slash sheets of IPC
4101B for thicknesses above and below .50mm. The test method used to
determine maximum moisture absorption is IPC-TM-650 Method 2.6.2.1.
Refer to paragraph 3.12.1.1 of 4101B.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Richard Kraszewski
Sent: Tuesday, May 29, 2007 9:53 AM
To: [log in to unmask]
Subject: Re: [TN] PWB Moisture Diffusion Rates
I'd be real appreciative of getting details on this topic also. Seems
that everyone agrees that mositure is detrimental for a PCB on multiple
levels but good documented evidence, & studies seem to be short supply.
BTW- One recent study on this subject was however presented at APEX this
past year by Paul Hamilton of Intel.
Rich K / GTS
847-621-7310
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gumpert, Ben
Sent: Tuesday, May 29, 2007 8:16 AM
To: [log in to unmask]
Subject: [TN] PWB Moisture Diffusion Rates
Fellow Technetters,
Anyone have data on moisture diffusion in and out of various PWB
materials? For various thicknesses, geometry, layers?
Is anyone treating boards differently through any processes, such as
duration and temperature of pre-build bake, or maximum time allowed out
of packaging before baking (for initial build or hand soldering /
rework) based on material or physical dimensions?
Ben Gumpert
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