wa2sff@hound.UUCP (J.WILKES) (01/27/89)
The standard method to repair intermittents is to alternately heat up and cool down the circuit. Heating is easy using a soldering iron or heat gun. However, the can of "freeze" stuff I had contained freon. Since it is now positively known that freon destroys the ozone layer what chemical or process can I use to cool a PC board down. Does anyone have any ideas or know of non-freon based "freeze"? Joe Wilkes att!hound!wa2sff
hwt@bnr-public.uucp (Henry Troup) (02/01/89)
In article <2910@hound.UUCP> wa2sff@hound.UUCP (J.WILKES) writes: >Does anyone have any ideas or know of non-freon based "freeze"? > This is a real problem - As Joe says, freon is nasty to the ozone. The previous "Solution" to the freezer spray was vinyl chloride - a carcinogen. Dry ice would do to cool the whole board, but not readily usable for component by component testing. utgpu!bnr-vpa!bnr-fos!hwt%bnr-public | BNR is not | All that evil requires hwt@bnr (BITNET/NETNORTH) | responsible for | is that good men do (613) 765-2337 (Voice) | my opinions | nothing.
ornitz@kodak.UUCP (barry ornitz) (02/02/89)
In article <2910@hound.UUCP> wa2sff@hound.UUCP (J.WILKES) writes: >The standard method to repair intermittents is to alternately heat up and cool >down the circuit. Heating is easy using a soldering iron or heat gun. >However, the can of "freeze" stuff I had contained freon. Since it is now >positively known that freon destroys the ozone layer what chemical or process >can I use to cool a PC board down. >Does anyone have any ideas or know of non-freon based "freeze"? The component "freeze" sprays are generally dichlorodifluoromethane, often called Freon-12 or Refrigerant-12; they are one member of a family of fluoro- carbons usually known as Freon. Unfortunately the same chemical inertness that makes it safe for electronic applications (non-flammable, low toxicity) also makes it linger in the atmosphere for years before reacting to harmless products. During this time, it can interact with the UV-ozone reactions in the upper atmosphere. There are other chemicals with similar boiling points to CCl2F2 that might be used as refrigerants in closed systems such as ammonia, sulfur dioxide, propane, and butane. All of these, however, have severe problems with toxicity, reactivity, or flammability. Liquid carbon dioxide, as in the CO2 fire extinguishers, might be a good choice but high pressures and extremely low temperatures are involved. None of these materials are suitable as direct replacements for Freon-12 in freeze sprays. The best solution I can suggest is to use a voxtex cooler. These units run on compressed air, needing several cubic feet a minute at 50 to 100 psi. They produce a stream of cold air at one end and a larger stream of hot air at the other. Several companies make these units specifically for the purpose you describe. One comapny that comes to mind is Vortec corporation; they make several units capable of reaching -40 degrees (C or F - same thing!). If you look up vortex coolers, you may find them listed as Hilsch tubes coolers. Barry WA4VZQ ----------------- | ___ ________ | | | / / | | Dr. Barry L. Ornitz UUCP:..rutgers!rochester!kodak!ornitz | | / / | | Eastman Kodak Company | |< < K O D A K| | Eastman Chemicals Division Research Laboratories | | \ \ | | P. O. Box 1972 | |__\ \________| | Kingsport, TN 37662 615/229-4904 | | -----------------
Dick@cup.portal.com (dick a wotiz) (02/02/89)
hwt@bnr-public.uucp writes: > In article <2910@hound.UUCP> wa2sff@hound.UUCP (J.WILKES) writes: > >Does anyone have any ideas or know of non-freon based "freeze"? > > > > This is a real problem - As Joe says, freon is nasty to the ozone. > The previous "Solution" to the freezer spray was vinyl chloride - > a carcinogen. I recently saw a DuPont advertisement for what they claimed to be a replacement for Freon, in freeze sprays and other aerosols. It is called Fluorinert, and supposedly doesn't damage the ozone layer or have any other side effects. (We'll see....) It's not an entirely new product; they've been using Fluorinert as coolant in Cray computers for a while. I don't know if it's on the market yet, or what DuPont's plans are for it. But if it replaces freon, I'm certainly looking forward to it. Dick Wotiz dick@portal.com {uunet|sun|atari}!portal!dick
cgs@umd5.umd.edu (Chris Sylvain) (02/04/89)
In article <1677@kodak.UUCP> ornitz@kodak.UUCP (barry ornitz) writes: ] In article <2910@hound.UUCP> wa2sff@hound.UUCP (J.WILKES) writes: ]] [...] ]] Does anyone have any ideas or know of non-freon based "freeze"? ] ] The component "freeze" sprays are generally dichlorodifluoromethane, often ] called Freon-12 or Refrigerant-12; they are one member of a family of fluoro- ] carbons usually known as Freon. Unfortunately the same chemical inertness ] that makes it safe for electronic applications (non-flammable, low toxicity) ] also makes it linger in the atmosphere for years before reacting to harmless ] products. During this time, it can interact with the UV-ozone reactions in ] the upper atmosphere. ] ] [...] As I learned from an atmospheric chemist (and from a short research paper I wrote), the reason R-12 (or CCl2F2) lasts so long in the atmosphere is that there is no chemical "handle" in the lower atmosphere that can break up the molecule. There are two notable refrigerants with nearly the same refrigerant effect as R-12, and very similar chemical non-reactivity: R-22 (CHClF2) and R-134A. R-134A is expensive (I don't have the paper in front of me, and I don't recall the formula for R-134A). R-22 has been produced for many, many years. The difference is that R-22 is a hydrochlorofluorocarbon. The hydrogen atom gives nature a handle on the molecule, so its lifetime in the lower atmosphere is greatly reduced. ..then there's the less saturated (carbon bonds) cousin of a CFC that was/is? used as a propellant in whipped cream containers that is as toxic as phosgene.. -- --==---==---==-- .. and shun the frumious Bandersnatch! .. ARPA: cgs@umd5.UMD.EDU BITNET: cgs%umd5@umd2 UUCP: ..!uunet!umd5.umd.edu!cgs
kluksdah@enuxha.eas.asu.edu (Norman C. Kluksdahl) (02/04/89)
In article <4495@umd5.umd.edu>, cgs@umd5.umd.edu (Chris Sylvain) writes: > In article <1677@kodak.UUCP> ornitz@kodak.UUCP (barry ornitz) writes: > ] The component "freeze" sprays are generally dichlorodifluoromethane, often > ] called Freon-12 or Refrigerant-12; > > As I learned from an atmospheric chemist (and from a short research paper > I wrote), the reason R-12 (or CCl2F2) lasts so long in the atmosphere is that > there is no chemical "handle" in the lower atmosphere that can break up > the molecule. There are two notable refrigerants with nearly the same > refrigerant effect as R-12, and very similar chemical non-reactivity: > R-22 (CHClF2) and R-134A. > > The difference is that R-22 is a hydrochlorofluorocarbon. The hydrogen atom > gives nature a handle on the molecule, so its lifetime in the lower atmosphere > is greatly reduced. > There is a very good paper, for those of you who care, about the effects of flourocarbons on the ozone layer, and the chemistry and atmospherics of their interaction. It may not be easy to find--it's in the Jan-Feb 1989 issue of American Scientist, published by Sigma Xi, by F. Sherwood Rowland. My opinion, for what it's worth (and I realize that this may seemingly have little to do with sci.electronics), is that we should all be conscious of the 'coolant' products which we are using. This is, however, sometimes difficult, as locating 'thermal' chips requires spot cooling on the pc board. If we can't avoid flourocarbons completely, let's at least minimize their use. (And that is the extent of my environmentalist soap-boxing.) Norman Kluksdahl Arizona State University ..ncar!noao!asuvax!enuxha!kluksdah standard disclaimer implied