Hi Ingemar! I'll assume that your CBGA has a 90Pb10Sn solderball which would account for a large enough source of Pb to allow for the formation of PbCO3. What is puzzling is that Sn preferentially oxidizes before Pb which I would think would inhibit the formation of PbCO3 (e.g. competing surface species growth reactions). What type of environment is the CBGA exposed too? I can't image your stock room being an environment to promote the growth of PbCO3. What are the CBGAs stored in? Have you conducted an FTIR test to see if there is a flux residue film on the CBGA solderballs after cleaning? Oh, do you have any of your usual cool photos of the PbCO3 that Steve can post? Dave Hillman Rockwell Collins [log in to unmask] "Ingemar Hernefjord (KC/EMW)" To <ingemar.hernefjo [log in to unmask] [log in to unmask]> cc Sent by: TechNet <[log in to unmask]> Subject [TN] PbCO3 08/31/2006 03:20 AM Please respond to TechNet E-Mail Forum <[log in to unmask]> ; Please respond to "Ingemar Hernefjord (KC/EMW)" <ingemar.hernefjo [log in to unmask]> 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------