This is generally caused from a residue of the antifoam chemistry in the
LPI developer. Heat/flux bring out the white scummy look. If you bake
the board @ 250F+, the white haze will go away.
Jeffrey Bush
Director, Quality Assurance and Technical Support
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302-1890
Tel. 802.257.4571.21 Fax. 802.257.0011
[log in to unmask]
http://www.vtcircuits.com
-----Original Message-----
From: Morse, Carrie [mailto:[log in to unmask]]
Sent: Wednesday, April 21, 2004 2:36 PM
To: [log in to unmask]
Subject: [TN] White Discoloration -- Excessive Heat, Insufficiently
Cured SM, or, Both?
We are wave soldering a LPI board and seeing a Whitish Discoloration --
Haze like -- only in the areas that the board has seen OA flux and wave.
We are using a wave pallet and the areas not exposed do not exhibit this
phenomena. This board is also processed through SMT for one side and we
do not see this around any of the SMT.
We have not seen this problem in the past, and, the Wave operator states
that the wave recipe has not changed.
So, I am wondering -- if LPI is not fully cured, will it turn white when
exposed to OA flux and Wave? Also, what IS the max temp LPI should be
able to see and for how long without discoloring? We've done an Acetone
test, but, it comes up clean and....I think I read in a previous posting
that the Acetone may not be an effective test for LPI. Is that true?
If so, What IS an effective test?
I'm headed to the Omega tester to see "how clean" the board is.
All advice is welcome!
-Carrie
---------------------------------------------------
Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
