TECHNET Archives

October 1999

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Lustig, Steven K.." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 15 Oct 1999 11:02:36 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (88 lines)
Richard,

Our goal in baking the boards is to remove moisture which may lead to
delamination during reflow or wave.  If after baking the boards are stored
in a drybox and then only taken out for processing (paste application, part
installation) then you should be fine.  The amount of moisture that has bee
re-absorbed will be minimal.  If, however, you keep the boards out in the
air for awhile (some number of days, I am not sure how many), then you are
correct, you will take in all of that moisture again.

As far as moisture sensitive components are concerned, we  bake those which
are susceptible to "popcorning" when they go through the reflow oven.

I agree that we should minimize the number of bakes and thus work to keep
the moisture from getting into the boards in the first place.

I hope this helps.

-Steve


Steven K. Lustig
Process Engineer
EMS Technologies, Inc.
Norcross, GA
(770) 263-9200 x4714
[log in to unmask]


-----Original Message-----
From: Richard Tilbrook [mailto:[log in to unmask]]
Sent: Thursday, October 14, 1999 11:16 AM
To: [log in to unmask]
Subject: Re: [TN] Board Delamination . . . RT


Steve,
If you vacuum oven your boards (boiling off and evacuating any moisture),
then open them into an environment, perhaps 22deg.C and 60%RH, won't the
boards quickly absorb the moisture in that environment? If you then
manufacture the boards, then ATE and inspect them, then conformal coat /
dip them, you'll be sealing moisture in.

I only ask because I am researching into moisture sensitive components,
and one of the options is to put the components into a vacuum (oven /
chamber).

I am concerned that putting non-hermetically sealed electronics
components (boards or devices) into a vacuum oven leads to little or no
advantage, and only the acceleration of intermetallic formations between
copper and tinned layer as a result.

My question (finally) is would this be the case? Or would the rate of
absorption be so slow that it wouldn't really matter?

Regards,

Richard Tilbrook

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################

ATOM RSS1 RSS2