Being the Indium Corporation, we know what indium is, where it comes from, and how to use it. But sometimes we forget that not everyone is as immersed in indium as we are.
So what is indium? Of course it is an element with an atomic number of 49, an atomic weight of 114.818amu, a relative density of 7.31g/cm3, and a melting point of 157°C. I have known that for most of the 27 years I have worked at Indium Corporation, but what exactly does that mean?
Well, the atomic number is important because it is the number of protons in the nucleus - and this is what gives each element its physical characteristics. It also places it in the periodic table (directly to the left of indium on the chart is cadmium which has an atomic number of 48 and to the right is tin, which has an atomic number of 50). This puts indium in the group of metals known as "Other Metals", along with bismuth, tin, zinc, antimony, gallium, and germanium. The atomic weight is a measurement of the total number of particles in the nucleus of the atom. If you want to know more about protons, electrons, and neutrons, go to the Jefferson Lab site.
The specific gravity or relative density of an element, which, in the case of indium, is 7.31g/cm3, depicts its relative density compared to water. If the relative density of an element is less than one, then it will float in water. If it is greater than 1 then it will sink. If you compare indium's relative density to that of lead, which is 11.35, you will see that, if you had a piece of each material cut to the exact same dimensions, the lead would be heavier than the indium.
Between the atomic number and the specific gravity, I use the specific gravity more often. It is used in a formula to find the weight of a solder part, or of a length of wire or ribbon.
So where does indium come from? Since indium is an element, it comes from the earth's crust. It is generally refined as a by-product of zinc ore mining. There is an ongoing debate about the availability of indium. But a lot of work is being done to create more efficient extraction methods and reclaim, particularly of ITO targets, to assure an adequate indium supply for existing and emerging technologies for decades to come.
Okay, now for the fun part. Where is indium used? It would probably be shorter to say where it ISN'T used! If you are involved in any of the following areas, you have a need for indium:
- Cryogenic sealing
- Hermetic sealing
- Low temperature soldering for temperature sensitive devices
- Step soldering
- Coatings for displays and glass (ITO & IGZO)
- Pb-free soldering
- Fuses
- CTE mismatch when bonding dissimilar materials
- Thermal management
Indium is certainly one of the more versatile metals because it works and plays well with others. Read more about indium: