I've a few different projects using the MCF51QU family of controllers. I received the uControllers sealed to protect against moisture. I've opened the package and used them as I need them. The package has not been resealed and I have not baked them after they were exposed. It appears that almost all of them are failing. In some cases they will work for minutes and in other cases for hours. One or two has not yet failed. At first I though it was a poor quality PCBs that caused the problems (e.g. float grounds). However in other projects the same happens. I either used a solder iron or reflow soldering to solder. The outcome is the same. Any advice on what could the problem be? Can it be moisture? What's strange though is that the uControllers work for a while and then fail. If the silicon cracks due to internal moisture one would expect them to fail immediately. I've never experienced problems with uControllers not resealed. Can it be a bad batch?
Any advice will be appreciated.