Yves/Paul: - The basis for the limitation on repairs was (like many other former requirements) based on a requirement from the U. S. Military. The rationale behind the limitation on the number of rework/repair actions stems from the concept that additional heating cycles increase the thickness of the intermetallic, thereby decreasing the long term reliability and limiting the number of field repairs possible before the intermetallic increases. - Given that a surface starts clean/bare, is subjected to tinning or HASL (1), is pretinned in house prior to assembly (2), soldered on a wave solder machine (3) [or dual wave machine (4)], then subjected to rework or repair (4 or 5), you can have as many as 4 or 5 heat applications to the materials before they are ever deployed to field service. Given that DOD equipment was (before Commercial Off The Shelf) COTS) designed with a 20-year life expectancy and a certain number of field repairs were anticipated, it was necessary to minimize the intermetallic to the greatest degree possible before the equipment was deployed for use. The DOD folks also did a lot of agonizing about the older solder-cut-solder systems (which engender an additional heat cycle) before biting the bullet and agreeing that users of a solder-cut-solder system would not be penalized by losing one rework opportunity. - In today's world the U. S. DOD is mandated to use COTS when available and avoid referencing the former (canceled) military specifications and standards. Since most COTS has a design life of substantially less than 20-years, and since field repairs are minimal (usually throw away and replace) the importance of minimizing the number of rework/repair actions is reduced. - Absent any requirement to the contrary you can pretty much rework/repair as many times as you want, unless of course your conscience causes you some problem. Regards, Jim Moffitt, Moffitt Enterprises Consulting ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################