I am looking for a material that is thermally conductive, but electrically insulating.

I need a thin sheet of this material to electrically Isolate my transistor from the heat sink without hampering the heat transfer...I tried Mica ..is there something better?

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110100101108 years ago
there are silicon pads and bolt isolators in most computer power supplies. go to a computer repair center and get some blasted power supplies synthetic machine oil is good substitute to thermal compound on computer cpu. i think it should be electrical isolator too. maybe paper soaked with oil is ok for your needs. but - oil does not live long and tends to stick to dust etc if its not sealed tightly between 2 parts (like cpu and cooler)

This claims to be the highest thermal conductivity dielectric. https://www.linkedin.com/pulse/litecool-trials-new-dielectric-material-black-x-james-reeves

Wyle_E7 years ago
The most thermally conductive electrical insulator is beryllium oxide.  It has the thermal conductivity of metaliic aluminum and the electrical conductivity of aluminum oxide.  Insulating washers of this material are available to fit most bolt-down  transistor and diode cases, and this is the only practical way to use it, since BeO is a hard and very refractory ceramic.  Note that BeO dust is carcinogenic.  It's not hazardous in pieces too large to accidentally ingest, but don't even think of grinding a notch in a BeO insulator to fit an odd corner.
lemonie8 years ago
Mica may be your best bet since you already have some. You could try splitting it into thinner slices and then using some silicone heat-transfer compound. Why is it necessary to electrically-isolate the two - these usually work as they are, or the heat-sink isn't electrically connected to something else? L
vinod nicholas (author)  lemonie8 years ago
The heat sink is screwed to the chassis of the equipment
Is there electrical conductivity through the heat sink to any of the transistor pins? Silicon can be an insulator too - so you may not need to do this.

DrBrown8 years ago
Alex-sharetskiy is right. Use the right thing for the job. Why screw around with electricicy and heat. These are both known components of rapid hair styling. You're not going to improve on the heatsink compound that every industy in the world uses.
Maybe thermally conductive ferrite?
Here's a web site that offers free samples:
what you are asking for is kind of difficult to find, because thermal and electrical conductivity tend to go hand in hand. This is because moving electrons can carry a significant amount of heat with them. If the temperature is not to high you might try a thin plastic film like you would use to cover food.
What you say is true for metals, but not for other materials. Diamond is both extremely thermally conductive as well as electrically insulating -- the "perfect" BCC crystal structure propagates phonons at high velocity and low dispersion, but there are few free electrons for conduction.
kelseymh8 years ago
Diamond is an excellent choice, if just a bit expensive. See http://en.wikipedia.org/wiki/Thermal_conductivity. You may also try a Google search for "thermally conductive insulator".
Sandisk1duo8 years ago
radio shack has some heatsink compounds
NachoMahma8 years ago
. Try this search: Mica +substitute. You'll have to wade through a bunch of gun stuff.