the thickness of oxide layer may also contribute to the color.
jk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Maguire, James F
Sent: Wednesday, April 09, 2003 4:11 PM
To: [log in to unmask]
Subject: Re: [TN] Blued solder joints
Charlie,
In my former job (at Boeing) we supported a military customer and after
converting from 1,1,1 to saponification they “noticed” an “increase” in
blue solder on sn/pb eutectic solder joints (both SMD and PTH). We
spent a small fortune on analysis (surface chemistry, chemical
extraction/FTIR, SEM, etc.) and found when all was said and done that
the “blue” flecks were related to the laminar spacing of the “beta”
phase (dark bands) in the alpha phase background. Basically, their
spacing was almost exactly the wavelength of blue light, thus white
light hiting these portions of the solder joint essentially hit a
structure that would reflect back blue light.
I don’t have the final report (of course) but if you like you could
contact Victor Starkovich at Boeing and ask him if they’re willing to
share this info. Was an interesting study.
You could reach Victor at 253-657-9125.
==============================
Jim Maguire
Intel Corporation
DuPont Site Environmental Lab
2800 Center Drive MS DP1-107
DuPont, WA 98327
email: [log in to unmask]
Ph (253)371-4065
Fax (253)371-5779
Pg (888)341-8572
======================================
-----Original Message-----
From: Charlie Pitarys [mailto:[log in to unmask]]
Sent: Wednesday, April 09, 2003 12:56 PM
To: [log in to unmask]
Subject: [TN] Blued solder joints
What would be the cause of blue tint, hue, specks etc to be visible on
the surface of solder joints. Is it just alloy composition?
I have seen this in the past typically in high temp reflow /high lead
alloy, copper lead frame devices around the die attach fillet.
Now it is being seen on a 63/37 alloy solder smt reflow.
It was not seen in the past, the cleaning chemistry is buffered to
protect the metal etc. and has been in use for many years without seeing
this phenomena!
Maybe if a crappy traditional high ph saponifier was used and the solder
joint was dull and gray it would not be as noticeable?
Perhaps the copper is leaching to the surface from the tinned component
lead or HASL surface?
My suspicion is that trace amounts of copper is present on the surface
of the solder joint after reflow. That when exposed to reflow
temperatures it picks up this bluish color.
Charlie
---------------------------------------------------
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
-----------------------------------------------------