At some point water from the humidity in the air gets into molded tantalum capacitors. Dipped tantalum capacitors fail because of other mechanisms.
Moisture is the death of a lot of stuff. Sometimes before it is even assembled. A lot of parts now are packed at the factory with descant so that they will stay dry. Failure to dry them before soldering can cause the parts to break like popcorn. Electrolytic capacitors tend to dry out. The electrolyte evaporates or reacts with the metal in the capacitor and the part becomes a resistor or worse the electrodes react chemically. I could go on but there are people who have said it better. NASA has done extensive studies on MBTF and MBTT. It is possible to make things that last for millions of hours. There are design patterns you can use to make that happen. On Wed, Dec 3, 2014 at 3:19 PM, Ron Bean <bucketwo...@rbean.users.panix.com> wrote: > Jon Elson <el...@pico-systems.com> writes: > >>One other place the military screwed up, is Tantalum >>capacitors. These have the >>bad characteristic that they can be VERY reliable if used >>CONSTANTLY. That means >>either on all the time, or used every few days. But, make >>something with >>tantalum caps, test it rigorously, and then put it in a >>supply depot for a couple >>years, and you will almost CERTAINLY find the caps short out >>and blow (as >>in fire and smoke) when you then put it into use. > > Does that mean that unused tantalum capacitors have a limited > shelf life? > > Also, Wikipedia says that some of them used to have a liquid > electrolyte, does that affect the shelf life? > > > ------------------------------------------------------------------------------ > Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server > from Actuate! Instantly Supercharge Your Business Reports and Dashboards > with Interactivity, Sharing, Native Excel Exports, App Integration & more > Get technology previously reserved for billion-dollar corporations, FREE > http://pubads.g.doubleclick.net/gampad/clk?id=164703151&iu=/4140/ostg.clktrk > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- Home http://evanfoss.googlepages.com/ Work http://forge.abcd.harvard.edu/gf/project/epl_engineering/wiki/ ------------------------------------------------------------------------------ Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server from Actuate! Instantly Supercharge Your Business Reports and Dashboards with Interactivity, Sharing, Native Excel Exports, App Integration & more Get technology previously reserved for billion-dollar corporations, FREE http://pubads.g.doubleclick.net/gampad/clk?id=164703151&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
