Hi folks - one additional possible root cause that is also related to cleaning. If the cleaning system/chemistry is too aggressive or if the pwa is over cleaned (say, like 10 exposures!), you actually produce a lead (Pb) rich solder joint surface with has a "blue/purple' optical effect in contrast to a normal solder joint which is tin rich. We used SERA analysis a few years ago to demonstrate this effect. Doug and I have also published the information in a couple of ppts at conferences - we call such pwas "Barney Boards" (Barney, as in the purple dinosaur on children's television). The optical effect is completely cosmetic and can be eliminated by reflow the solder joints. I'll see if I can post the pictures. Dave Hillman Rockwell Collins [log in to unmask] Brian Ellis <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 08/13/2011 01:41 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Brian Ellis <[log in to unmask]> To <[log in to unmask]> cc Subject Re: [TN] Blue solder joints This is most likely due to having a cleaning process that is almost too good! Most commonly seen after some kind of aqueous cleaning, followed by drying at temperatures above 60-70°C. The cleaning will leave unprotected metal (if it were solvent cleaning, it would leave a protective monolayer on the metal). The metal will then oxidise during the drying. I've seen this hundreds of times. Brian On 12/08/2011 21:56, Gumpert, Ben wrote: > Technetters, > > I seem to remember this coming up previously, but I couldn't find it in the archives... What causes solder joints to have a blue tint? > > I have a card where most of the solder joints across the assembly have a blue tint to them. It's Sn63Pb37 solder on a SnPb HASL board and a variety of part finishes - but the pads that weren't pasted don't exhibit the blue color. This is the only card in the lot that has this condition, but I don't know what process it may have seen differently from the others. > > Some kind of oxide? > > Thanks in advance, > Ben > > > ______________________________________________________________________ > This email has been scanned by the MessageLabs Email Security System. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 16.0 > 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 > For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 > ----------------------------------------------------- > ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------