I quit using "freeze cans" for troubleshooting because they did not work very well particularly on conformally coating products.
When a "thermal failure" occurs it happens at a particular temperature
or during a specific temperature change. Because polymers
require much more time to change temperatures I discovered that freeze
mist would "shoot by" or run past the thermal failure point.
It would then require a long time to stabilize the circuit and try
again. I used the EXair because I could control
the temperature change by varying the distance from the nozzle to the
circuit, had an endless supply of "cold", air and very little if any
frost/moisture on the circuit. I discovered that 90% of the thermal
failures could be "found" by recreating the thermal conditions at time
of failure and gradually "bumping" the temperature around this point. I
seldom had to go more than + 20 degrees C from the estimated thermal
fail point to recreate the failure.
Conformal coatings will "hold" joints in place until a certain thermal
point is reached. Usually this is a "window" because as the coating dimensions
change
the joint will "make and break" contact.
Hope this helps!
David A. Douthit
Manager
LoCan LLC
Carl VanWormer wrote:
According to the site:
http://www.emsdiasum.com/ems/clean/duster.html
The stuff I'm using claims "100% ozone-safe pressurized duster products".Since I turn the cans upside down (or refill my quick-freeze cans for a more
convenient spraying position), am I being more gentle to the environment?
If so, we can get down to the real question of "am I wrecking my electronics
systems by using quick-freeze for troubleshooting?"Carl Van Wormer
Cipher Systems
1815 NW 169th Place, Suite 5010
Beaverton, OR 97006
Phone (503)-617-7447 Fax (503)-617-6550-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Friday, April 26, 2002 2:52 AM
To: [log in to unmask]
Subject: Re: [TN] Freeze Spray Trouble ShootingBev
I agree PFCs are the worst climate changers (with SF6) that exist. Some
of them are over 10,000 times worse than CO2. As a rule of thumb, 6
freezing cans which contain a PFC gas would have as much effect on
climate change as a medium car over its whole lifetime (horrific
thought). Furthermore, there will still be the contents of two of those
cans in the atmosphere 40-odd generations from now (assuming man lives
for another 40 generations!). However, I think most freezing cans
contain HFC-134a, which is bad enough but not as bad as PFCs. Some may
still contain HCFC-22 which is just as bad AND an ozone depleter, to
boot, but is not phased out under the Montreal Protocol until 2010 (some
countries may phase it out sooner).Brian
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