I have been unable to locate a system assembly level spec that details allowable warp and bend of an SMT PCBA while it is being installed into a chassis of some kind. I have concerns of potential fractures of SMT solder joints if the PCBA is allowed to flex "too much" due to installation of daughtercards, I/O cards, power cords, etc...but have no idea how much is "too much". Based solely on flexing some out-of-date circuitry with my bare hands, it seems evident to me that it doesn't take much flex or bend to create an open or intermittent circuit connection. To give you a visual idea of the kind of flex I am looking at that many of you may be familiar with, consider pushing the power supply cable connectors of a PC power supply into an IBM PC Compatible motherboard...there are generally speaking, one or several 208-pin PQFP's in the area as well as numerous SOICs, R's and C's. Can anyone point me toward an allowable flex spec for a PCBA in order to eliminate the incidence of assembly and handling induced SMT joint problems? [log in to unmask]