Bev, thanks for your detail on this. One additional consideration is cost and availability of a replacement assembly. Bottom line--every soldering temperature excursion has a detrimental effect on the assembly. Maybe a little or maybe a lot (see Bev's list of variables). There was an Air Force spec that limited the number of rework/repair operations, but unless every assembly has a unique serial number and there is a complex, globally accessible database, how will a person know if a particular component has already been removed/replaced three times? Yes, depending on the skill of the technician, there may be evidence of a rework but three times will look the same as one time. Any limitations have to be established by a product owner based on info that only they know, it isn't possible for the IPC committees to set those limits. Cordially, Jack Jack Crawford, IOM IPC Director Certification and Assembly Technology [log in to unmask] 847-597-2893 FAX 847-615-5693 3000 Lakeside Drive, Suite 309 S Bannockburn, IL, 60015 -----Original Message----- From: Bev Christian [mailto:[log in to unmask]] Sent: Tuesday, August 07, 2007 8:53 AM To: TechNet E-Mail Forum; John Burke Subject: RE: [TN] Rework question John, I am having people look, but if there is a limit I do not remember. However, from a practical point of view, the answer is Doug Pauls' patented (Or is that copyrighted or trade marked? Being a lawyer, I don't know.) phrase, "It all depends". It depends on the method of rework, (reflow, wave solder, selective soldering, soldering iron, hot air gun focused IR, flame), temperatures reached, ramp rates, dwells, size of board, thickness of board, type of component, heat sinks, skill of operator. I could go on. Make yourself a fishbone diagram. And then are we talking about say 3X of the same component, or 5X side-by-side or 7x but each in a thermally separated area from the other six? Here's a scenario for you: double sided reflow and then required rework under cans on both sides of the board. So this means two more for can removal, dressing the can pads, removing the components, dressing the pads, part deposition, can replacement. And hope everything works! So you need visual inspection, x-ray inspection, electrical test and if you really want to do it right, x-sectioning and a whole battery of reliability testing. I have seen good work and I have seen thin boards delaminated after a single, poor attempt at rework. Bev RIM -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke Sent: Tuesday, August 07, 2007 10:29 AM To: [log in to unmask] Subject: [TN] Rework question Hi, I had a question yesterday which was "has the number of re-work cycles allowed by IPC changed for lead free?" And I confess I don't know but I bet someone on this link does. If you could let me know number of thermal cycles allowed and the spec reference I would be grateful. 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