At 08:00 PM 8/27/99 -0700, you wrote: >I just received some Ramtron FRAM chips (FM25040-P's) from Future >Electronics. The chips are sealed in a de-aired plastic package along with >what appears to be a dessicant pouch. And there is a warning that says: > >"CAUTION This bag contains moisture sensitive devices" >It goes on to state that shelf life in the bag is 12 months at <<40 degrees C >and <<90% relative humidity (RH). It then says that chips not immediately >mounted after removal from the bag must be baked and it has a schedule of >baking options. There are no instructions suggesting what the life span of >chips are after mounting, which is curious, since merely soldering the leads >on the chip does not protect the chip from moisture. > >Is this warning message: >A) the work of prankster >B) some paranoid label that gets put on all bags leaving Future Electronics >C) a real warning, in which case Ramtron is severely misrepresenting its >products. Ramtron makes no mention of humidity sensitivity on the data >sheet for the chip. The plastic encapsulating the chips absorbs water. With DIP parts this is usually not a problem since they are wave soldered in production and the case doesn't get too hot. It is a REAL problem with tiny SMT parts--I have seen them explode when the hot air hits the parts and they get hot. Its the moisture turning to steam. This does NOT effect the parts in operation--only during assembly. Manufactureres always recommend an overnite bakeout of SMT parts going into automated assembly. I haven't had a problem (Knock on wood) yet with hand assembly. BUT I keep the parts in the bag with the desiccant any way, and work in an environment with fairly low humidity to begin with. It doesn't hurt, and may definitely help. Moisture CAN effect systems that are operating on VERY low power or analog stuff that has very high input impedances--moisture will adsorb or absorb as the case may be and form leakage paths. Washing and baking my PCB's dry after assembly will cut power draw from 50 to 30 uA in many cases. Enjoy, kelly William K. Borsum, P.E. -- OEM Dataloggers and Instrumentation Systems < & <