Indium
Indium is a chemical element with the symbol In and atomic number 49. Indium is the softest metal that is not an alkali metal. It is a silvery-white metal that resembles tin in appearance. It is a post-transition metal that makes up 0.21 parts p ...
is a soft, malleable, silver, shiny metal with atomic weight of 114.82 and resides as number 49 on the Chemical Periodic Table. Below 3.4Kelvin indium is a superconductor and at 20 C it has a resistance of 8.8 micro-ohms with a melting point of 156.598 C, a boiling point of 2080C and a density of 7.3 g/cc. Indium can be alloyed with a wide range of other metals to lower their melting point.
Indium is an ideal thermal interface material for heat dissipation in many of today's very hot integrated circuits. Of all the common materials, copper and aluminum have the highest
thermal conductivity
The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa.
Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...
. But on the micro level most materials are very rough and a two piece sandwich of copper may not have a good conductive path between them. To overcome this limitation, indium is the ideal material due to its high bulk thermal conductivity (86W/mK) and its soft compressibility allowing it to fill voids in rough surfaces. In addition, as a seal indium will not pump out or dry out. In fact, indium has the unique ability to cold weld two dissimilar materials if the materials have a thin coating of .002”-.003” of indium they will ‘cold-weld’ together if the clamping pressure is more than 40 psi.
When indium is compressed its bulk thermal conductivity of 86 W/mK pushes down the resistance at the interface to be much lower than greases, fluids, or adhesives. For high power applications there is no better thermal interface material than indium due to its high conductivity, low tensile strength, and ability to alter melting point of alloys, in addition to indium's ability to dissipate great amounts of heat away from sensitive devices.
Applications
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Vacuum seals
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Cryostats
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Dilution Refrigerators
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Optical Windows
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Lasers
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
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Cryocoolers
A refrigerator designed to reach cryogenic temperatures (below ) is often called a cryocooler. The term is most often used for smaller systems, typically table-top size, with input powers less than about 20 kW. Some can have input powers as lo ...
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Cold Heads
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Thermal links
Technical Information
* Groove Design
PRODUCTION RATE FOR (5 OZ.) 140 GRAM INGOT
SIZE LGTH FT./OZ. GR./FT. AREA GROOVE 'D'
'W' (sq. in.) 80% 90%
.020"(0.5mm) 300' 60' (20'/$100) .46 .000314
.030" 135' 27' 1.04 .000706 .020" .021"
.040" (1.0mm) 75' 15' 1.88 .001256 .025" .028"
.050" 50' 10' 2.80 .001962 .031" .035"
.060"(1.5mm) 35' 7' 4.00 .002826 .038" .042"
.0625" 32' 6.4' 4.37
.070" 26' 5.2' 5.38 .003846 .044" .049"
.080"(2.0mm) 20' 4' 7.00 .005024 .050" .056"
.090" 15' 3' 9.33 .006358 .056" .064"
.100" 12.5' 2.5' 11.2 .007850 .063" .070"
.125" 8' 1.6' 17.50 .012265 .078" .088"
.1875" 44" 8.76" 38.35 .027597
D=Half dia. +.005>.015 min.
Rectangular groove dimensions:
epth x Width = .80min. x cross section
References
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Indium