I can puzzle out how you could get carbonate but not how you would get lead
carbonate. Lead is unreactive compared to other metals present and they
would react in favour of the lead, or even if the lead reacted would
displace it in the corrosion cell reaction.
If you are getting significant carbonate formed so quickly then this would
imply a fairly high acidity on the work, which is hard to relate to that
found in electronic grade fluxes.
You have nothing to lose by trying an activated rosin base flux to reduce
this stuff -whatever it is - and floating it away as a slag/dross in the
rosin, but I doubt it would be effective unless you re-melted the solder. If
you were to do that it would be similar to some purification processes for
solders [and other metals,]
Regards
Mike Fenner
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
Pb-free: www.Pb-Free.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ingemar Hernefjord
(KC/EMW)
Sent: Thursday, August 31, 2006 9:21 AM
To: [log in to unmask]
Subject: [TN] PbCO3
We got lots of such growth on CBGA balls recently. After
soldering/cleaning: nada. After one week in stock: signs of growth.
After one month: unacceptable crystals. Now, being insoluble in water
and many solvents, some specialists advise you to mix an RA with
ethanol, heat this mixture and dip the part until the crystals vanish.
My question to TN is whether there is alternative methods? Some accept
PbCO3 growth as being harmless, but this is not our intention, because
loose particles are semiconducting and can create leakage current paths.
Brian's book "Cleaning and Contamination of Electronics and Assemblies"
mention there are five groups of white residues, but, oddly enough, lead
carbonate is not included. The chemistry world of soldering residues is
so complicated, that I have to ask you for help.
Thanks in advance
Ingemar Hernefjord
Ericsson Microwave Systems
---------------------------------------------------
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
-----------------------------------------------------
***This email, its content and any files transmitted with it are intended solely for the addressee(s) and may be legally privileged and/or confidential. If you are not the intended recipient please delete and contact the sender by return and delete the material from any computer. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited.
Messages sent via this medium may be subject to delays, non-delivery and unauthorized alteration. This email has been prepared using information believed by the author to be reliable and accurate, but Indium Corporation makes no warranty as to accuracy or completeness. In particular, Indium Corporation does not accept responsibility for changes made to this email after it was sent. Any opinions or recommendations expressed herein are solely those of the author. They may be subject to change without notice.***
---------------------------------------------------
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
-----------------------------------------------------
|
