A couple months ago we jointly commisioned a professional and
independent H.A.L.T test (highly accelerated life testing) be run on
our TS-7250 design with one of our customers to find out just how
rugged our boards are. A link to the 32 page officially prepared
report is at ftp://ftp.embeddedarm.com/halt.pdf. The operator at the
facility was quite impressed with the board and said he's rarely seen
anything so ruggedly built.
Tests they ran:
*) extreme high/low temperature runs
*) rapid thermal tests (getting the board to about boiling temperature
and then super cooling it with liquid nitrogen)
*) vibration (G force) tests
*) combined (vibrating while in hot/cold temps.. etc..)
A few highlights:
*) Even though the intention of the test was to test the board until
they broke, they were unable to destroy a single TS-7250. Actually,
the vibration table they were using started malfunctioning before
anything on the board did. The operator had said a previous test on
another board actually caused it to "explode" as parts of the board
started flying off with high velocity.
*) A +70degC rated TS-7250 board actually continues to work properly
from -60degC(-76degF) to +110degC(230degF). At the high end
temperatures, the epoxy inside the null modem cable started melting
and seeping out yet the board continued to run fine. At the low end
temperatures frost and snow was forming on the board. These
temperatures were where the boards started exhibiting strange
behaviors... once the temperature was brought back down between
-60degC and 110degC, they snapped back to life without any permanent
damage.
*) Board was still holding together at 55 G rms. What we found was
that if you are in a *extreme* high vibration environment, you
probably want to solder down the power connections and use a dab of
loctite on any DB9 screws (since they have a tendency to unscrew at
extreme G force ratings), but otherwise the board will be fine. USB
also is a non-industrialized connector (figures since it comes from
the consumer PC world) and shouldn't be used in high vibration
environments-- but everybody probably knows this.
*) The fast temperature cycles caused *nothing* to go wrong. This is
quite surprising as this is one of the most brutal things you can do
to a board. Keeping the number of passive devices to a minimum and
hand-routing the traces on the board paid off here.
All in all, a very impressive result. I wish we could have tested one
of those "embedded" PC motherboards (EPIC, mini-ITX, etc..) alongside.
Most of those boards have large, heavy heatsinks/fans attached that
would have been fun to watch cause the circuit boards to shatter or
pull off the solder pads on the attached chips. Also, since they're
not thermally stable enough to go without their heatsinks/fan at room
temp, its likely an overtemp condition would result in thermal runaway
and eventual permanent self-destruction.
//Jesse Off
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