There are known compatibility issues with some alloys and joint configurations and in your case you would have determine the unknown ones. My question to you would be: Why go there? 1) ROHS allows the use of leaded solders for repair of pre ROHS products. 2) Infrastructure [power stations ] is presently excluded from ROHS along with anything else where high reliability is required (Aviation, medical, automotive etc). 3) Suggest that even assuming Pb free solders were environmentally superior (and some doubt this), in your application the environmental impact of using Pb-free solders would be negligible and far outweighed by the possible consequences of unreliable joints. Regards Mike ü Please consider the environment before printing this e-mail -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Goodyear, Patrick Sent: Sunday, May 01, 2011 7:12 AM To: [log in to unmask] Subject: [TN] Repair / Rework on non-in-house RoHS compliant boards As a technician that does frequent board level repair rework some questions have come to mind. While the majority of my work is legacy i.e. vintage (1968) we will face these concerns in the near future. The boards I primarly work on are Nuclear graded Class IE, (high reliability, seismically qualified, etc.) high dollar boards, typically in the 3-10g range and are not throw-aways, most have components that are no longer manufactured. I am looking to the industry to find best practices, this is one of the places that was suggested for posting. Any help you can give me would be appreciated. With pre RoHS solders most if not all of major manufacturers used 63/37 solders and repair rework was easy, one just used 63/37. With the adoption of RoHS controls and the subsequent use of many different alloys of lead free solders, (at least 6 I know of), the following comes to mind: 1. Are there compatibility issues mixing between the various alloys of lead-free employed currently in electronics manufactures? In strength and reliability primarly. 2. How does the technician determine the correct alloy of lead-free solder to use? 3. How does the technician determine what alloy was originally used by the manufacturer? 4. Will IPC 7711A / 7721A standards be updated to delineate alloy determination and / or an alternate methods for the complete removal of lead-free solders and subsequent repair using 63/37 or lead-free alloys? Pat Goodyear Control Technician Pacific Gas and Electric Company Diablo Canyon Nuclear Power Plant PO Box 56 Avila Beach, CA. 93424 805-545-4312 ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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