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I want to measure heatsink temperature using LM35 TO-92 package. heatsink is a flat surface of aluminum.

What is the proper way of mounting a TO-92 temperature sensor on a heatsink so that can measure the temperature of the surface of heatsink and also not fall off easily?

ElectronSurf
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    check this link: http://tech.mattmillman.com/an-easy-way-to-mount-ds18b20-temperature-sensors/, i think this is exactly what you need. – Cheche Romo Feb 19 '20 at 17:45
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    @ChecheRomo using an extra clip may bring additional Rth which may lead to incorrect measurements because there's no guarantee of perfect thermal coupling between the two metals. Instead, "fastening" *(e.g. via a glue-like material like epoxy)* the chip directly onto the heatsink will bring the best result. – Rohat Kılıç Feb 19 '20 at 18:36

2 Answers2

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Heatsinks do exist for TO-92 packages. Use the parametric search at your favorite components supplier and look for Thermal Management > Heat Sinks > Designed for or Package Cooled and select TO-92.

Here are some examples:

  • Aavid Thermalloy MAX12NG (rail mounted clip for TO-92 sensors)
  • Aavid Thermalloy 575200B00000G (slide-on heatsink)

(The second link is less a datasheet and more a catalog.)

However, I think your question title is somewhat misleading. You're not trying to cool the TO-92 device (the LM35), but rather sense the temperature of some other heatsink with it.

The TI LM35 datasheet under Layout Guidelines states:

The LM35 is easily applied in the same way as other integrated-circuit temperature sensors. Glue or cement the device to a surface and the temperature should be within about 0.01°C of the surface temperature.

Given that information, you might also want to look for thermal epoxy and adhere the device to the surface you intend to measure. MG Chemicals, 3M, Wakefield-Vette, and many others make such epoxies. With this in mind, you should be able to find application information and datasheets to accomplish your goal.

JYelton
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Among other packages, LM35 comes in TO-220. This package is a better option for measuring temperature of a heatsink. It has a metal tab with good thermal conductivity, and it has a mounting hole. Depending which net your heat sink is connected to, you may need a heatsink mounting kit.

If you have a choice, use LM35 in a TO-220 package for measuring temperature of a heatsink.

Nick Alexeev
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