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I want to screw a heatsink to my LD1117V33 voltage regulator. It's a normal 3mm screw and nothing inbetween. Do I need to use thermal paste or something like that?

It will be regulating 12V down to 3.3V to power an ESP-12F which will controll three MOSFETs to control my LED strips.

Thank you!

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  • \$\begingroup\$ You should use paste for best effect. Or a thermal pad if the tab is electrically connected to a pin. \$\endgroup\$
    – DKNguyen
    Commented Jun 17, 2019 at 15:01
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    \$\begingroup\$ Page 6 of DS: The TAB is connected to the VOUT \$\endgroup\$
    – Andy aka
    Commented Jun 17, 2019 at 15:07
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    \$\begingroup\$ By the way, did you notice that the thermal pad on the LD1117 is at output voltage (Vout) ? Make sure that the heat sink isn't connected to some other net. The heat sink may be arranged such that it's floating. More on that here. \$\endgroup\$
    – Nick Alexeev
    Commented Jun 17, 2019 at 15:09
  • \$\begingroup\$ @NickAlexeev No, thanks for the heads-up, I'll need to check that out once the PCB is here (not my own design), but afaik the heatsink won't be connected to anything else. I guess a thermal pad won't suffice for insulation, since the screw conducts electricity too? \$\endgroup\$
    – matthesinator
    Commented Jun 17, 2019 at 16:47
  • \$\begingroup\$ @matthesinator If you ever need to insulate the heatsink, you can use a metal screw with a special plastic shoulder washer. This is often called heatsink mounting kit. \$\endgroup\$
    – Nick Alexeev
    Commented Jun 17, 2019 at 16:56

1 Answer 1

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Thermal paste will give better thermal transfer between two objects. Rarely are objects flat, this means that only a fraction of the area is being used for heat transfer. And heat transfer depends on the area and the material (thermal grease has a much higher thermal conductivity than air). So use thermal grease or a thermal pad for best results.

Thermal pads usually have a lower thermal conductivity and conduct heat less. Almost any kind of metal will increase the thermal dissipation to air.

A good idea would be to calculate the heat that needs to be dissipated in the first place. Take the voltage drop of the regulator and multiply it by the current and that should give you the thermal dissipation number.

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    \$\begingroup\$ It's worth noting though, that you may get away just fine without thermal paste if the amount of heat to be dissipated is small enough. Especially if this is a hobby project and may be torn apart for parts later, not having thermal goop on the heatsink could be handy. A thermal pad would get around that fringe limitation though. \$\endgroup\$
    – Hearth
    Commented Jun 17, 2019 at 15:36
  • \$\begingroup\$ As I said, it will be used to regulate 12V down to 3V. I don't know the amperes, but will measure it when I have all the materials here and connected on a breadbord or so. Although I think that a microcontroller won't pull too much \$\endgroup\$
    – matthesinator
    Commented Jun 17, 2019 at 16:51

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