Lee, If both of the alloys will mix thoroughly during re-flow, it shouldn't make much of a difference whether you solder SAC balls with the eutectic paste, or vise versa. Regards, Vladimir ------Original Message------ From: Lee Whiteman Sender: TechNet To: [log in to unmask] Subject: [TN] SnPb SOLDER BALLS WITH SAC SOLDER PASTE Sent: Dec 8, 2009 08:17 I know about the problems with soldering BGAs with SAC solder balls and SnPb solder paste and read plenty of papers pro and con. I heard about a report where if you solder BGAs with SnPb solder balls using SAC solder paste, the resulting solder joint will be unreliable. Has anyone heard of anything like that? If there are any cross-sections or papers that you can share with me, that would be great. Thanks again. Lee Whiteman, PMP Senior Member Engineering Staff L-3 Communications East Telephone: (856) 338-3508 FAX: (856) 338-2906 E-Mail: [log in to unmask] SENTEC 11 Canadian Road, Unit 7. Scarborough, ON M1R 5G1 Tel: (416) 899-1882 Fax: (905) 882-8812 www.sentec.ca