Just to clear up the confusion from the previous responses: To my knowledge, the IBM PowerPC components are ceramic ball joint arrays (CBGAs) that utilize a Pb90 ball, not Sn90. The melting temperature of these primarily lead balls is way up over 250 deg. C. They are not intended to be brought into liquidus. These lead balls are attached to the CBGA package with Sn63 solder, and they are intended to be used with standard Sn63 solder paste to form the SJ to the pads on the assembly. Ceramic-body CBGAs typically use Pb90 solder balls because the lead balls have a higher modulus of elasticity, providing some strain relief between the very low CTE of the alumina oxide component and the higher CTE of a standard FR-4 PWB. Because the Pb90 BGA balls do not go into liquidus, but the Sn63 paste does, a small amount of the lead ball dissolves into the molten Sn63 to form the solder joint. It is important, however, to either increase the standard reflow profile and/or the MRT slightly to get good wetting of the Sn63 solder over the Pb90 ball and get a good homogenous mix, but you do NOT need to melt the Pb90 ball. I have found that if you attempt to use the standard reflow profile you will get what Mr. Macko is seeing, good wetting on the board pad, but not quite perfect on the Pb90 ball. Increasing the TALT or the MRT slightly (perhaps by 10 deg. C) usually fixes the issue. If your IBM PPC CBGAs do in fact have Sn90Pb10 solder balls, then you would use a Pb-free profile with enough TALT and a high enough MRT to form a good homogenous SJ. I do not have any experience with soldering Pb90 CBGAs with lead-free solder, but I assume the principle is the same as soldering with Sn63. However, with the higher temperature lead-free profile and using a Sn99 solder, I am assuming more of the lead ball will be dissolved into the solder joint, and the homogenity will be less, which will result possibly in a solder joint of lesser reliability. But I may be wrong about that. Others with experience in this care to comment? -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Macko Sent: Friday, February 27, 2009 10:04 AM To: [log in to unmask] Subject: [TN] Reflowing CBGA component (with high Sn balls) using Eutectic solder paste Hi All, My question is related to the soldering of IBM PPC CBGAs type components (that have Sn90Pb10 solder balls) using Sn63 paste onto ENIG finished boards. What are the "determining-factors" to improve the wetting/diffusion of the eutectic solder paste into the high Sn solder balls. The eutectic solder appears to wet well to the ENIG pads located on the board but occasionally I see eutectic solder fillets that do not always appear to fuse well with the high Sn content balls (if fuse is the correct word?). thx Best Regards, -Joe "This e-mail and any attachments are solely for the use of the addressee and may contain L-3 proprietary information that may also be defined as U.S. Government export controlled technical data. If you are an unintended recipient of this e-mail, use, disclosure or distribution of its content is prohibited. Please notify the sender by return e-mail and immediately delete this message." --------------------------------------------------- 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 -----------------------------------------------------