The size of the LF BGA (thermal mass) is important consideration before starting this process. Small BGAs (DDRs) are an easy decision than 1000 and more LF BGAs mix profile process. Best Regards Reuven ROKAH e mail: [log in to unmask] Think green before printing this mail... Thanks -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Tuesday, October 21, 2008 9:38 PM To: [log in to unmask] Subject: Re: [TN] Lead Free BGA'S Hi Richard - your comments provide good additional ideas to keep in mind. The folks at Celestica (Dr. Polina Snugovsky and crew) have published a couple of papers since my paper first was released to the public which are very good and give a better overall bandwidth discussion on the different aspects of achieving good solder joint integrity in a mixed situation. One issue I know that all of the "camps" include in their discussions is the impact of the increased reflow temperature on the integrity of the tin/lead solder process qualified components. Your "Camp C" option is a good attempt to find a solution and balance all of the competing advantages/disadvantages. Richard Coyle published a good paper at the 2008 SMTAI Conference with contained some excellent data on the impact of mixing. I am hoping that we get a few more papers this year from the industry research that show the impact of a hybrid situation in a product type test. Dave "Stadem, Richard D." <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 10/21/2008 12:03 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to "Stadem, Richard D." <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] Lead Free BGA'S I echo Dave Hillman's response, with some additional considerations. I am of Camp C, which sort of agrees with Camp A and also Camp B. But Camp C is very concerned with trying to reflow lead-free BGAs using a 63/37 paste and profile, albeit slightly higher, which I think is the "hybrid" reflow profile which John's assembly house is probably using. The concern here is that the circuit board material and the components themselves were probably not selected and/or qualified to be subjected to the higher reflow temperatures and longer times needed to achieve the completely mixed (homogenous) alloy. In addition, I know of no studies or industry data that tested this particular alloy combination. I would have to say that if you are attempting to reflow this combination, and are also using ENIG as a surface finish, the risks of running into issues with the solder joint reliability, the via reliability, and the rest of the component's reliability are stacked against you. I cannot say enough good things about Dave's paper on the subject. I used it as a reference document in my paper published in this month's Circuits Assembly magazine. I think if you read both papers you will come away with a better understanding of the risks of assembling the Pb-free BGAs using leaded solder. What will become very clear to you is that you should never attempt to do this without fully qualifying the process to ensure you are not doing something harmful to the rest of the components and/or the circuit board itself, so you do not end up with a huge problem later. As you can see by some of the other respondents, that is what happened to them, and they are certainly not the only ones that this happened to. I have been called in to look at this issue more than once, and it gets real expensive in a hurry. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Tuesday, October 21, 2008 11:23 AM To: [log in to unmask] Subject: Re: [TN] Lead Free BGA'S Hi John! Well, I have a response that probably isn't what you are looking for - " it depends" (cha-ching, Doug gets another Mt. Dew). There are two basic camps out in the industry: Camp A: don't use a lead-free BGA in a tin/lead solder process because you just don't know what the resulting solder joint may be; (2) Camp B: increase the reflow temperature so that the lead-free BGA in a tin/lead solder process can reach a uniform distribution of Pb throughout the solder joint. Some of the published reports also indicate that the BGA construction specifics (i.e. material type, die size, I/O, ball metallurgy, e.g.) can play a significant role in whether the solder joint integrity would be compromised. The 2006/2007/2008 SMTAI Conference proceedings are good sources of published papers on the topic. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] John Foster <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 10/21/2008 10:21 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to [log in to unmask] To [log in to unmask] cc Subject [TN] Lead Free BGA'S Our assembly house recently assembled some boards with Lead Free BGA's for us and when I asked them if they used a lead free process they responded with. We use leaded solder (Sn63Pb37) with a hybrid oven profile to accommodate the lead-free BGA. I hope this answers your question. Please let me know if you have any more questions." Is this a common process, is this a reliable process Any input is appreciated Thank You John Foster --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 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 15.0 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 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 15.0 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 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 15.0 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 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 -----------------------------------------------------