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Thermal paste or silicone tape ?

Discussion in 'd.i.y.' started by Gervais Cote, Jul 21, 2021.

  1. Gervais Cote

    Gervais Cote Predator

    Hi gents,

    I'm just wandering if these two methods to allow heat transfer from output transistors to heat sink are both as good as each other.

    I am more familiar with the thermal paste and when rather new and applied properly it transfers the heat very well but I'm a bit skeptical about the efficiency of the silicone tape.........

    Worst case, is it a good idea to use both the silicone tape AND thermal paste or I should stick to the existing heat transfer method only ?

    For those not familiar with the silicone tape, here is an example :


    Thanks in advance.
  2. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Unless it's for a class A amp it doesn't matter.... and if both done optimally it still doesn't matter!
    Gervais Cote likes this.
  3. Puggie

    Puggie Well-Known Member

    Mica and silicone grease is better, but that tape you show looks like keratherm, and it's pretty good too, for a hell of a lot less mess. If you are not running the transistors on their bleeding edge thermally, kerathetm should be fine.
  4. martin clark

    martin clark pinko bodger

    That's a very old Hitachi Mosfet (2sk227)

    If it has lived this long mounted /in use like that - it is doing just fine, leave it be : )
    CJ14 and Gervais Cote like this.
  5. sq225917

    sq225917 Bit of this, bit of that

    For a less than perfect surface, keratherm everytime
  6. Tony L

    Tony L Administrator

    In that image isn’t the tape also acting as an electrical isolator?!
  7. Gervais Cote

    Gervais Cote Predator

    Good point ! I’ll put it stay away from a firework !
  8. Yank

    Yank Bulbous Also Tapered

    As does the mica wafer...
    Gervais Cote likes this.
  9. davidsrsb

    davidsrsb pfm Member

    Getting good quality mica is not easy these days.
    If you are not sure what you are doing, leave power transistors alone.
    It is very easy to get a burr or swarf from the screw hole puncture the insulator.
  10. CJ14

    CJ14 Retired

    I use ceramic and silicon grease.

    Insulators Part Number - 4180G Aluminum Oxide Ceramic Aluminum oxide insulating washers have a dielectric strength of approximately 21.7 x 103 volts/mm for .76mm material (550 volts/mil for 0.030 inch materail) and 16.9 x 103 volts/mm for 1.57mm material (430 volts/mil for 0.062 inch materail). The thermal conductivity of aluminum oxide is 15.06 W/mK at 75° (167° F) [8.71 BTU/hr-ft° F]. Aluminum oxide has unique thermal conductivity qualities and features low loss factors at high frequencies. It has high compressive strengths, high volume resistivity, low thermal expansion and it resists radiation. Note: Hole diameters are +/- .13mm (.500"), angularity is +/- 1° and flatness is .05mm (.002") TIR unless otherwise specified.
    quickie likes this.
  11. russel

    russel ./_dazed_and_confused

    Is that an MF P170?, to your question silicone pads are the easiest to use, as has been pointed out make sure the surfaces are smooth, I use emery paper, wash the surfaces and visual inspection and never lost a transistor in forty odd years of DIY and I hate anything mechanical.
  12. Gervais Cote

    Gervais Cote Predator

    Yes it’s a P170 in rather great condition but in need for a recap and a few new resistors that got some heat. Trafos are from 1987 but final assembly was done in 1988. Can’t wait to hear it !
  13. sam_cat

    sam_cat C'est Crounchifique!

    If it matters, its all about W/mK.. Watts per meter-Kelvin.
    Higher is better, lower is worse.

    I tend to use Thermalright Thermal Pads which are 12.8 W/mK for anything thermally critical, thermal paste is generally better, and the cheap blue thermal pads are generally (a lot) worse.
  14. Burrrrrton

    Burrrrrton Member

    I would use what I am more used to working with. If you are used to thermal paste, use it.

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