ITO is commonly used to shield windows and anti-reflectance can be used to reduce glare. I suspect the rainbow is due to poor quality and not to all ITO coatings. The original patent holder of applying ITO to glass is Saleem Shaikh of Thin Film Devices in Anaheim. www.tfdinc.com. Copper tape is commonly used to ground the edges of the window with good results. Thin Film Devices can provide more information on thickness and shielding effectiveness if interested. They are a privately held applicator of these types of coatings.
Regards, Steve Toyama 925 447-1200 From: "Chris Maxwell" <[email protected]> To: "John Woodgate" <[email protected]>; <[email protected]> Sent: Friday, September 17, 2004 6:10 AM Subject: RE: Germanium & ITO Window shielding effectiveness > Whew, > > Everybody is on the beam. > > My two or three sentence reply has brought up a few questions. Let me > just say that I take no exception to anybody debating me regarding > electromagnetics...even though my surname is Maxwell. The genes have > thinned out over a few generations; so I make many "debateable"...even > "questionable"...or "wrong" judgements :-) > > For Mr Woodgate: Did I mean mu-metal? > > No, I meant monel. I put the question mark after it because I knew > that it was available as a shielding material; but unsure of its > permeability. According to Laird technologies website, monel contains > Copper Iron and Tin. I assumed that the Iron would impart a > permeability higher than 1. > > Will mu metal shield low frequency better than monel? Sure. But I > haven't seen any mu-metal mesh screens for windows. I also don't know > how expensive a mu metal mesh screen would be if you could get one. > > For Mr. Javor: > > 14 Ohms/square vs 14 Ohms /square inch... You're right, it's 14 > Ohms/square. At what thikness of ITO? The usual thickness applied. I > don't apply it; you would have to ask someone that applies it...for > instance Chomerics (or whatever they are now called, these companies > change names faster than I change beard styles). > > Will ITO provide some shielding? Sure 14 ohms/square will provide an > impedance mismatch with air. You'll get some reflection of plane waves. > But think about some of the other requirements of good shielding. A > well shielded enclosure needs to treat seams and aperatures so that they > won't radiate according to Babinet's principle. For instance, consider > a metal enclosure with an ITO coated window. As surface currents flow > on the enclosure, they will encounter the window. Most of the current > will flow around the window, since the conductivity of the metal is > orders of magnitude below the ITO. When the current flows around the > window, you have charge acceleration (it changes direction)...which > yields radiation. This is why I said ITO isn't so great for shielding. > It provides some, but not much. > > Is 14ohms/square a higher conductivity than what's needed to dissipate > static.? Sure you could dissipate static with a lower conductivity > coating; but would it be as transparent as ITO? (Indium Tin Oxide by > the way for readers who are wondering). That's why I consider ITO a > good static dissipative coating. > > > How about some tips from experience, since we've used ITO: > > 1. ITO can cause rings to appear on a window due to refraction (you > know those little rainbow rings you see if you put a little oil or water > between two pieces of glass). This isn't always a problem. It can > happen if you sandwich an ITO coated window with another, or if you put > an anti-glare coating on an ITO coated window. We had the > anti-glare/ITO coating problem. Our display had little rainbow rings > all over it. > > > 1-a. See above. We once had the rainbow ring problem and had a bunch > of windows we wanted to rework (i.e remove the ITO). The windows were > lexan with ITO coating. We had to scrap the windows since we couldn't > find a solvent that would remove the ITO while leaving the lexan intact. > > > 2. ITO can be expensive, but any window shielding can be expensive. > > 3. ITO can be hard to bond to the bezel. > > 4. We were paying about 20-30 dollars for an ITO coated lexan window > over a 8" display. Once we passed compliance testing, we went back to > look at cost reductions. We tried a display windo with no ITO coating. > Our results were just as good (this doesn't mean it didn't provide any > shielding, it just means it didn't provide much; and the display wasn't > a problem area). We were able to eliminate it and bring our window cost > down to a few dollars. > > 5. ITO definitely has a low relative permeability; so it will have > problems with absorbing magnetic fields. ITO definitely has a low > conductivity, so it will have problems reflecting magnetic fields as > well. (it won't readily form eddy currents) > > > So, will ITO provide some magnetic shielding?...sure...but not much. To > me, it falls into the category of a marginal fix. If you have a window > that needs just a little bit of shielding to pass and you have no other > option...then ITO is OK. > > However, if you need some serious shielding, you'll probably need to > look at a wire mesh window insert. If you need some serious magnetic > field shielding, then try to find a wire mesh window insert with a high > permeability. > > Of course, these are just my own opinions. > > Chris Maxwell > Nettest > > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/listserv/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
