What do you call thermal pad that electrically isolates

[drakejest]

I would like to buy some thermal pads that also electrically isolates them to the heatsink. What do you call them

I need to cover a 75mm by 250mm area, I would like to attach a fanless powersupply to the case and since the case is sealed, hopefully lets sa case acts as a heatsink.

[bjbb]

Look at products from companies such as Bergquist and Laird.

All you had to do was search for something such as 'thermally conductive insulator' or go to the product search for some one like Digikey or Mouser or even Walmart.

[drakejest]

Look at products from companies such as Bergquist and Laird.

All you had to do was search for something such as 'thermally conductive insulator' or go to the product search for some one like Digikey or Mouser or even Walmart.

A great idea, i found one  that looks really nice but could not identify if they are electrically conductive

this graphite based one seems to be the best at thermal conductivity but if affraid if its electrically conductive can you check it out

[TimFox]

The data sheet shows its electrical conductivity as 10⁵ S/cm = 10⁷ S/m, approximately that of graphite, while copper metal is approximately 6 x 10⁷ S/m

[TimNJ]

"Sil-pad" is often the term used for a thermal pad between some TO-*** package and heatsink. These are electrically isolating.

https://www.henkel-adhesives.com/us/en/products/thermal-management-materials/sil-pad-materials.html

[pqass]

According to https://sound-au.com/heatsinks.htm#s7 Kapton (polyimide) tape/sheet has a similar thermal resistance to Sil-Pads.  Not cheap for the area you have in mind.

[drakejest]

The data sheet shows its electrical conductivity as 10⁵ S/cm = 10⁷ S/m, approximately that of graphite, while copper metal is approximately 6 x 10⁷ S/m

Im sorry i dont understand what those units means, what does S stands for?

but look at it, am i right to asssume the thing is 6 time less conductive than copper? so for example if copper has a resistance of 10ohms for a given area the graphite has a 60 ohms worth of resistance?

[TimFox]

“S” means “Siemens”, the modern term for inverse ohms.  So, your calculation example is correct.  Back in the day, we called that unit “mhos”, ohms spelled backwards and abbreviated as an upside-down omega.

[ajb]

According to https://sound-au.com/heatsinks.htm#s7 Kapton (polyimide) tape/sheet has a similar thermal resistance to Sil-Pads.  Not cheap for the area you have in mind.

Kapton's not that expensive. McMaster-Carr has 12"x12" 1 mil sheets for $12. Laird sell a polyimide film pre-coates with a ceramic phase change material which is quite convenient if the mating surfaces are flat, called Tgard K52. I think it's like $30 for an ~11x18" sheet or something. If the surfaces aren't flat enough for that to work well you can also apply your own thermal compound either side of the plain film, the conductivity of the compound doesn't matter at that point as long as it doesn't bridge over the edge of the film. But it's probably not worth using anything fancy anyway, the regular silicone stuff is probably fine since you have the polyimide film in the anyway.

[pqass]

According to https://sound-au.com/heatsinks.htm#s7 Kapton (polyimide) tape/sheet has a similar thermal resistance to Sil-Pads.  Not cheap for the area you have in mind.

Kapton's not that expensive. McMaster-Carr has 12"x12" 1 mil sheets for $12. Laird sell a polyimide film pre-coates with a ceramic phase change material which is quite convenient if the mating surfaces are flat, called Tgard K52. I think it's like $30 for an ~11x18" sheet or something. If the surfaces aren't flat enough for that to work well you can also apply your own thermal compound either side of the plain film, the conductivity of the compound doesn't matter at that point as long as it doesn't bridge over the edge of the film. But it's probably not worth using anything fancy anyway, the regular silicone stuff is probably fine since you have the polyimide film in the anyway.

Maybe it's me but I can't get over the fact that a roll of 3" wide Kapton tape is over CA$100! 
Although, you do get a 36 yards of it which makes it cheaper per sqin than the sheet you quoted.
My need just isn't that great and I haven't yet found a convenient source with the right quanity/$ for me.
Last week, I just bought some TO-247 sized thermal pads for ~CA$0.50 per piece.  I'm still bitter.