Sounds like one lot was not cured exactly as the other.

What you may be is moisture entrapped in the mask itself...take one of the
boards and bake it at a couple hundred degrees (if components will allow)
for an hour or two and see if the milky goes away.

I do not believe you are seeing a nonconforming condition, strictly visual.

Franklin

-----Original Message-----
From: Peter Lee [mailto:[log in to unmask]]
Sent: Monday, August 08, 2005 8:56 PM
To: [log in to unmask]
Subject: [TN] Solder Mask discoloration

Technet,



We have encountered what appears to be mask discoloration after wave
soldering.



The areas of concern coincide with the areas that were exposed selectively
by fixtures during wave soldering, dominated by one date code of PCB with a
slightly different green (lighter) solder resist. Other data code (same PCB
vendor) with darker solder resist waved at the same time have less/no
discoloration.



We have not seen this issue before this build. There was no PCB vendor
change & (known) process &.



Process details:

Reflow (x2 times)

Wave solder: preheat (120/130C), solder temp 260C, with fixture

Flux: no clean, halide free

Top side max PCB temp 110C

Wash&Rinse cycle 8min at 130F in DI with saponifier, Dry 1 min at 100F



Following link shows PCB images with white milky masks after wave soldering
AND WASH. It does not seem to be surface residues (IPA has no effect). PCB
vendor is currently investigating.



http://members.shaw.ca/ppwlee1/Images/Mask_color1.jpg

http://members.shaw.ca/ppwlee1/Images/Mask_color2.jpg

http://members.shaw.ca/ppwlee1/Images/Mask_color3.jpg



Has anyone seen this before? Any idea on what causes the mask discoloration
and its potential impact on the assembly?

Any comment is greatly appreciated.



Rgds,

Peter




---------------------------------------------------
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
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
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 847-615-7100 ext.2815
-----------------------------------------------------