Cold spray, where do you buy?

A few years ago i took my wife to the dermatologist.The guy just walked around with a bottle of liquid nitrogen zapping people. He took care of three place on my wife and hit me in five places even though I wasn't there as a patient.

Jimmie

Sounds like a nitrocidal maniac.

John

It's probably better to be all fingers than "all thumbs"?

Tim

What's so bad about mail order? If you can't tolerate mail order, wtf don't you post your locale?

Try holding most tools without using your 'opposable' thumbs.

Thanks, that is great, but I need it this afternoon and many shippers don't seem to like to transport this stuff anymore.

Nothing against mail order but I was told it won't be air-shipped. Plus I'd have needed it this afternoon. And we do not have a local newsgroup here. Is it so bad to ask whether one of the countrywide chains has it?

Yep, those are the ideas! :-)

We can have fun with this.

Maybe some pet shop has some poop freeze ? Maybe Wallyworld Got2B Glued Blasting Freeze Maybe some wasp freeze ? Maybe some horse Freeze-It® Spray

All Electronics MCM Newark Jameco Grainger

I coulda shipped it overnight yesterday. Too late.

We use Chemtronics Freez-It and some sort of duster spray. Neither tastes or smells bad. Maybe some people are putting nasties in theirs to discourage kids from snorting the stuff.

John

But, I always end up turning the duster upside down.

greg

If you have a local auto-parts, and preternaturally good ventilation, starting ether could serve in a pinch.

Or just sharpen an ice cube! ;-)

Good Luck! Rich

R134 from an auto parts dealer.

Next time you want some now, take a drive down the hill to Fry's.

Thanks, John, very kind offer. But it turns out the problem is deeper, the whole chebang gets overnighted to the chip manufacturer on Monday.

That's possible. As long as it isn't harmful I guess that's ok. It certainly discourages munching on stuff while working on circuit boards ;-)

Good hint, thanks. I wouldn't buy other stuff there but I guess with cold spray one can't go wrong.

I use freeze spray and heat guns for FPGA timing verification. Prop delays are a radical function of temperature. Last week I demonstrated to a consultant that he didn't have a speed problem, he had a logic problem. His crap flakey design didn't change at all when I froze the chip. Then I fired him.

John

I believe you, John, but being an analog kind of guy I can't reason why propagation delays are a radical function of temperature. Can you explain?

Jim

Well, that's CMOS.

I don't know the physics, but mosfet channel resistance and interconnect resistance have pretty strong positive TCs, so things get slow when they get hot. A reasonable path in and out of a Xilinx FPGA might take 5 ns, and its TC might be in the ballpark of 5 or 10 ps/K. In our delay generators, we generally have to compensate. Gluing a heat sink to the FPGA helps, and adds an air of mystery too.

One of my guys is going to engineering school part-time, and as a project he measured the prop delay TCs of some Xilinx chips in various situations. I'll post it if I can find it.

As I recall, TTL also slows down with temperature.

ECL hardly changes at all, under 1 ps/K for a typical EclipsLite gate.

John