Subject: | |
From: | |
Reply To: | TechNet E-Mail Forum. |
Date: | Mon, 13 Jan 2003 05:55:19 -0800 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
[Dehoyos, Ramon] My previous company sent coupons to be tested for
humidity and the lab sent us a chart. At 135 C the humidity chart was flat
in two hours. At 90 C it took about 6 hours to remove 90 percent of the
board's humidity. We bake the boards for 4 hours at 105 C. They are good
for three days, unless they are sealed in a bag with a desiccant bag ( do
not need to be vacuumed ) or stored in a dry environment. A room may be
conditioned to have low humidity and a 40 deg temperature where carts with
boards not fully populated can be walked in and stored. ( i.e. one side of a
SMT board was done and due to a reason the second side can not be done right
away).
Regards,
Ramon
> >
> > Fellow Techheads,
> >
> > I am continually being challenged about the amount of time &
> > temperature required to safely remove moisture from
> > multilayered FR4 bare boards so they can be safely populated
> > and reflowed. And, the time/temperature required to remove
> > moisture from a populated board when a BGA needs to be
> > replaced using a hot air rework station such as an AIR-VAC
> > DRS24. I realize that baking out boards at an elevated
> > temperature will degrade solderability with time as well as
> > age components so ideally boards should not be baked out any
> > longer than necessary.
> >
> > Everyone seems to have a slightly different idea of the time
> > vs. temperature required which generally ranges from 4 to 24
> > hours at temperatures as low as
> > 85 to 125 C. 85C definitely seems to low to me. IPC/JDEC
> > J-STD-033A list
> > bakeout times for components depending on thickness which
> > seems excessive
> > for a circuit board. I have not found any IPC guidelines for circuit
> > boards.
> >
> > Anyone like to comment on what has worked for them? Is
> > there an industry
> > standard out there? thanks in advanced for the feedback.
> >
> > joe
> >
> > ---------------------------------------------------
> > Technet Mail List provided as a free service by IPC using
> > LISTSERV 1.8e To unsubscribe, send a message to
> > [log in to unmask] with following text in the BODY (NOT the
> > subject field): SIGNOFF Technet To temporarily halt or
> > (re-start) delivery of Technet send e-mail to
> > [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE
> > mailing per day of all the posts: send e-mail to
> > [log in to unmask]: SET Technet Digest Search the archives of
> > previous posts at: http://listserv.ipc.org/archives Please
> > visit IPC web site http://www.ipc.org/html/forum.htm for
> > additional information, or contact Keach Sasamori at
> > [log in to unmask] or 847-509-9700 ext.5315
> > -----------------------------------------------------
> >
>
> ---------------------------------------------------
> Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
> information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> ext.5315
> -----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
|
|