View Full Version : Indium??????????????/

10-12-2008, 11:22 PM
I keep seeing ingots of indium for sale on ebay. What would someone use these for?

Bruce Griffing
10-12-2008, 11:25 PM
Indium is a good low temperature solder. You can also make a fairly decent solder bond to some glasses with indium.

10-13-2008, 08:48 AM
Its also used in any type of flat panel screen (laptop, TV, etc) to make the TFT (Thin Film Transistor) on the glass backing sheet.

10-13-2008, 09:27 AM
Bearing alloy additive for shell bearings. Duffy

10-13-2008, 03:39 PM
Since toy solders are cast from lead, I imagine toy Indians are cast from indium.:confused:

10-13-2008, 04:06 PM
In the old days, many ships were made from gallium, with the exception of the first ship to reach this continent- that was build from americum. A small part of the ark must have been made from boron.

Pardon me, I think a part of me must be made from moronium. :)

10-13-2008, 04:16 PM
But just remember, the king of all materials is unobtainum. For best hardness, use unobtainum carbide. Or for maximum bureaucratic effect, use administratium.

10-13-2008, 05:55 PM
Don't forget that all matter is made of particles that can't ever be seen or even exist in isolation. Then there is neutronium. It has a computed density of 10^14 grams per cubic centimeter. Pretty heavy stuff.

10-13-2008, 06:10 PM
Yeah, I've got a neutronium boring bar. It doesn't chatter, but it's a bitch getting it on the lathe.


Tim The Grim
10-13-2008, 07:38 PM
I used to build dies that would blank out pure indium discs. The material is like stamping baby poop. Most times it was about .003 thick and the discs were about a mm (.0394) in diameter. each die had a couple dozen punches and would run close to 300 strokes per minute. The discs had to be burr free and were then washed in trichlor and packaged in argon.

The customer would drop the discs through a neutral hydrogen flame and into columns of hot silicon based oil. As they sank through the oil, spheres would form and collect at the bottom. After some more cleaning the spheres were then used in machines that would place them on microelectronic circuits for precision soldering.

A couple tears ago indium was also listed by some health "Gurus" as one of those "miracle nutrients" that everyone needed to be healthy. I would not suggest taking a bite out of an ingot of baby poop as a healthy past time.

Bruce Griffing
10-13-2008, 07:41 PM
Indium, by itself, is not used in active matrix displays. Indium tin oxide is a pretty good transparent conductor and was used in the early days of active matrix displays. A variant is replacing ITO due to the cost of ITO. I think the replacement is a fluorine doped tin oxide, but I am not sure.

10-13-2008, 07:44 PM
I seem to recall something about it being used as a transition layer in some types of plating.

10-15-2008, 08:54 PM
Indium phosphide is one of the wonder semiconductors like gallium arsenide that never made it mainstream. It's got very high electron mobility, so it's great for high frequency ring oscillators, microwave and power electronics, and it's extremely radiation resistant, so it's sometimes used in aerospace applications.

But, like gallium arsenide, it's hole mobility is 8x lower than it's electron mobility, so Indium phosphide and Gallium Arsenide are almost always implemented in old-school NMOS technology (as opposed to balanced, CMOS == Complementary logic used in modern bulk silicon semiconductors), so Indium phosphide and Gallium Arsenide generate a tremendous amount of heat, and are impractical for most high-performance digital logic.

Indium phosphide and Gallium Arsenide semiconductors have been around for almost as long as bulk silicon, and every couple of years you'll see a DARPA proposal for a 600 Ghz supercomputer, but it never makes it off the drawing board because of it's thermal inefficiencies.

10-16-2008, 01:44 AM
Check this out. Soldering non-metallic items:



10-16-2008, 12:36 PM
That's pretty cool Jerry -- I'm guessing that's how indium is used in LCD displays:

Indium and high indium alloys will coat non-metallic materials when the molten metal is gently rubbed against the surface of the non-metal. Materials on which this coating ability can be utilized include glass, mica, quartz, glazed ceramics and certain metallic oxides.

Bruce Griffing
10-16-2008, 01:35 PM
I stand by my claim that indium, by itself, is not used in active matrix displays. Too expensive and no reason to do it. The cover glass is sealed to the base glass in an LCD using epoxy. In a past life I ran an early LCD fab, so I am sure about this.

10-16-2008, 02:01 PM
Sorry Bruce, I wasn't refuting what you had said -- just curious that Jerry's link showed that you can plate glass with indium. Pretty neat...

10-16-2008, 04:20 PM
Tin oxide works fine for many transparent conductor applications. It's used on CRT fronts to provide an anti-static coating, on the platen glass of high speed copiers to prevent static buildup and on the windshields/canopies of aircraft to make antennas, defrosting circuits and to deflect radar signals so they don't reflect from interior components like the pilot. There isn't any particular need to use indium in such applications as far as I know.