AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Leon Heller" <leon.heller@d...>
wrote:

> I've just had a Tiny11 prototype behaving very oddly. I wasted a lot
of time 
> with it, and then tried cleaning the flux off off the board (I often
don't 
> bother with prototypes). It immediately started working properly.
> 

Could be dendritic growth.  With the fine spacing on chips, 3V & some
surface contamination (flux harbouring moisture, oil, perspiration) is
sufficient to grow dendrites between pins. Once they form they may
short the pins, get toasted & leave a fine carbon trace or just
intermittently short & retreat according to humidity or board 
temperature.

When I fist saw a movie of this phenomenon it scared the hell out of
me as I live in a humid climate. Since then I have don't use
no-cleans or leave resin on the PCB.  You even have to be carefull
with lacquers as some absorb moisture.

Cheers

Don