Hi Phil! Take a look in the TechNet archives as this topic was ground thru pretty well a couple of weeks back but you do have a dilemma. The majority of the published literature shows that if you completely reflow the Pbfree solderball or allow diffusion to create a uniform microstructure then you will create a reliable solder joint. So the simple answer would be to just reflow your entire assembly using a Pbfree reflow profile - but - the moisture sensitivity levels (per JSTD-020B) for your Sn/Pb BGAs are going to most likely decrease a couple of levels (e.g. a MSL 1 could drop to a MSL 3). This decrease in MSL rating means you could be causing damage to the components by using the Pbfree reflow profile. I would recommend caution in running the Sn/Pb and Pbfree BGA components at the same reflow profile. Many companies are "rebumping" the Pbfree solderspheres with Sn/Pb solderspheres to avoid the issue. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] DUTTON Phil <Phil.DUTTON@TENI X.COM> To Sent by: TechNet [log in to unmask] <[log in to unmask]> cc Subject 02/10/2005 10:17 [TN] Mixing Lead free BGAs with PM normal BGAs Please respond to TechNet E-Mail Forum <[log in to unmask]> ; Please respond to DUTTON Phil <Phil.DUTTON@TENI X.COM> Hello, We've run into a problem where a PB Assembly will have a mixture of BGAs, some with regular tin/lead solder balls, some with lead free solder balls. This raises the question as to what temperature profile to run. Do we need to ask our loader to do a Pb free profile first, followed by a Pb profile? Or will it be ok to solder both together using the regular, lower temperature Pb profile? Personally I'd like to avoid the extra run through reflow. thanks, Phil Dutton C.I.D. --------------------------------------------------- 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 -----------------------------------------------------