Freeze Sprays

[Martin Czech]

> Hi
> 
> Sorry for the slightly off topic subject, but I am hopefully going to be
> using this information for work on my OBXa.
> 
> Could somebody please explain how a Freeze Spray can be used for fault
> finding.  It says you can on the tin but not how.  Does anybody have any
> info, or Web links.
> 
Not ot at all!!

Freeze Spray cools elements you spray via evaporation energy transport. So
if you suspect a thermal fault or if you want to know how a part behaves
during temperature changes, you can simply cool it down.

Example: A DSP is not able to run at 20MHz as it is supposed to be.
Cooling it down it will suddenly run (CMOS). Now you know that you have
made a design fault, some critical path is too long, and if the chip
runs hot it gets even longer (gate delays will approx. double from 0 to 120C)
 
Of course you can also check all kind of thermistors etc.

Sometimes you are able to make a faulty circuit run for a short while,
so you have at least a chance to see what is wrong...

And sometimes this is used for demos at industrial fairs, to make customers
believe that we have allready a working chip....

Attention: the exposed parts really cool down, far under 0C.
This means that you'll see ice, and later water, this could make some "leakage".

So, it is a quick tool, but not very precise.
For precise temp measurements you need a temp chamber or a thermostream.

m.c.