On a few electronics repair vlogs (e.g., Trevor Bench YT channel), the host notes he uses common high-temp silicone to adhere heat-sinks and RTDs.
This may not be a bad idea as long as the solidified silicone CONDUCTS "thermal energy" and not INSULATE. So the silicone needs to conduct like a mica washer or thermal paste.
All I've read about high-temp silicone notes it is an INSULATOR, not CONDUCTOR.
Not sure what this "repair tech" has in mind, but he does repeat the use in various repair videos, using stuff like

Neutral Cure Silicone https://www.chipquik.com/store/product_info.php?products_id=492007
Or "caulk tube" variety ...

 

Wakefield has a thermal epoxy.

 

You always want to use a substance between any module and its heat-sink with minimum thermal resistance, as high temperature is the enemy of semiconductors, and high temperature silicone does not necessarily meet that criteria.
Unfortunately many technical utube videos contain incorrect information generated by people with little technical training.

Always use a thermal paste or epoxy (as MrChips noted) for that purpose.

 

EDITED

The guy in that video is making a classic mistake when using any thermal compound, that is applying a copious amount.

The best thermal transfer is always from direct contact between the sink and the component, the compound is only there to correct imperfections and less is always more.

 

In another video that same vlogger uses ChipQuik Neutral Cure Silicone Adhesive Sealant to bond RTD to heatsink for an audio amplifier. Often, amps use RTDs as thermal trackers (for amp dynamic biasing), but they just "air couple" very close to heat sink (w/o any physical contact).

If you want to couple using stuff from Home Depotm perhaps the best metric to metric to compare is thermal conductivity from the datasheet.

3M Thermally Conductive Epoxy Adhesive TC-2810
https://multimedia.3m.com/mws/media/266197O/technical-data-july-2015.pdf?&fn=TC-2810-TDS.pdf
thermal conductivity (0.8-1.4 W/m-K)

So, maybe from Home Depot, JB Weld High Heat:
"J-B Weld epoxy, specifically the standard epoxy steel resin, has a thermal conductivity of about 7.47 W/(m·K), which is significantly higher than most epoxy resins but much lower than metals like aluminum or copper."

REFS:
https://www.masterbond.com/properties/thermally-conductive-epoxy-adhesives

 

to bond RTD to heatsink for an audio amplifier

Since an RTD doesn't dissipate significant power, using any standard adhesive is fine for mounting it on a heat-sink, since the its thermal resistance will have negligible effect on the temperature difference between the two.

 

Since an RTD doesn't dissipate significant power, using any standard adhesive is fine for mounting it on a heat-sink, since the its thermal resistance will have negligible effect on the temperature difference between the two.

If the adhesive is INSULATING, the RTD won't "feel" an accurate temp. metric. So biasing tracking will suffer.

 

If the adhesive is INSULATING, the RTD won't "feel" an accurate temp. metric. So biasing tracking will suffer.

Heat/thermal or electrical resistance insulation?

 

If the adhesive is INSULATING, the RTD won't "feel" an accurate temp. metric. So biasing tracking will suffer.

I believe you are confusing electrical resistance with thermal resistance.
It can be electrically insulating and still will have a low-enough thermal resistance to keep the RTD at the same temperature as the heat-sink.

 

I believe you are confusing electrical resistance with thermal resistance.

I believe you are speculating I am confused. IAC, see my OP.

 

I think a breakdown of the chemistry (active ingredients) of thermal epoxy for electronics is worth pursuing.
MG Chem sells a 2-part product.

"8349TFM is a 2-part, flame retardant, thermally
conductive epoxy adhesive. It is a dark grey,
smooth, thixotropic paste that cures to form
a hard, durable polymer that is thermally
conductive, yet electrically insulating.

This thermal adhesive is most often used to bond
heatsinks to CPUs, LEDs and other electronics
components. "

I can't find the exact chemistry of such products. Maybe MSDS:
https://www.mgchemicals.com/downloads/msds/01 English UK SDS/sds-8349tfm-part-a en uk.p

 

I believe you are speculating I am confused. IAC, see my OP.

I was replying to your Post #7 which seems to confuse the two.
Most things that are electrically insulating, are fairly heat conductive.