It doesn't Victor. The situation probably is that he's building assemblies that doesn't need to comply with RoHS, but the only BGA's that are available have lead-free spheres... -Steve- -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor G. Hernandez Sent: Thursday, November 16, 2006 10:01 AM To: [log in to unmask] Subject: Re: [TN] Separation in BGA joints Ioan, Early on the discussion you stated: "Due to pressures from our customers we run many lead-free BGAs on leaded paste at 220C. If this forms joints, why LF on LF would not form joints at 246C, or let's say 230C if I am really off in my temp measurements? " How does this comply with RoHS? Victor, -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan Sent: Thursday, November 16, 2006 8:12 AM To: [log in to unmask] Subject: [TN] Separation in BGA joints Thanks to everybody who replied, including the non-metallurgists ;-} I have certainly learned things! I think the secret lies in that 270C melting point. I use a regular SAC305 soldering recipe (right semantics, not profile; see, I got this one Werner), hence the 240C target peak. Of course this will not move the 1.75%Cu alloy. One thing is that the component data sheet says the alloy is SAC305. But it also recommends 260C for peak temperature. I find this very weird, since somebody told me we need to solder at MP + 20C, so my 246C should be more than OK. Not to mention that many ICs on the board are speced per J-STD-020C for max peak of 250C. Question 1: why this 260C recommendation, when 240C should be OK? Then, I would like to know more about the case of high temp solder balls. Why a joint will be formed around 210C between SnPb paste and 90/10 balls and the solder would not wet at 246C on a 270C solder ball? The flux cushion is there in both cases. And why the SAC ball should melt anyway, if solder wets on 90/10, why shouldn't it wet on other higher temp balls? Is it because the Pb goes into solution with the Sn whereas the high concentration Sn-Sn interfaces absolutely have to mix? Thank you very much, Ioan --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------