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This is different from a lot of other stuff here, but I have a motherboard that has no MOSFET cooling, and when I touch them they burn my hands; they are probably 70-80C.

I just want to know how long can the MOSFETs last under these conditions?

Mobo: Gigabyte 990FXA-D3

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Try to get the part number of the MOSFETs, and search the web, to get their datasheet.

Power MOSFETs are often rated for operation upto 125C or 150C, i.e. they could boil water and still be within normal operating conditions.

As Ignacio Vazquez-Abrams says cooler lasts longer. However, I would be surprised if a motherboard from a reputable manufacturer failed due to power MOSFETs first.

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  • \$\begingroup\$ it says nothing, the mosfets are just black, i think there is something written next to them but its to small to read it. \$\endgroup\$ – theraginggamer Sep 20 '14 at 15:48
  • \$\begingroup\$ @theraginggamer - really? It is sometimes hard to read. However, if that is the case, I would assume 125C. These datasheets chosen at random SiR890DP IRFHM8337TR are rated upto 150C \$\endgroup\$ – gbulmer Sep 20 '14 at 16:12
  • \$\begingroup\$ the board looks just like on the picture, here i can't really tell what it says next to the mosfets on my case because of the cooler that's blocking it \$\endgroup\$ – theraginggamer Sep 20 '14 at 16:45
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It depends on the heat rating of the MOSFETs. If they are getting that hot, then they can probably withstand that temperature also.

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    \$\begingroup\$ but if i were to put a heatsink over them, would that help with the lifetime of them \$\endgroup\$ – theraginggamer Sep 20 '14 at 14:05
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    \$\begingroup\$ Naturally, since a 10degC difference doubles the lifetime. But they'll probably still last very long as they are. \$\endgroup\$ – Ignacio Vazquez-Abrams Sep 20 '14 at 14:22
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Probably they'll last longer than the viability of a PC motherboard! If the internal (junction) temperature isn't much over 100'C they're in relatively conservative territory.

The electrolytic capacitors are usually the first parts to die, and that's usually after the motherboard is obsolete (5 years at least).

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  • \$\begingroup\$ mostly all motherboard now have solid caps, and even if they die you can replace them, you can't replace a mosfet at least not easily \$\endgroup\$ – theraginggamer Sep 20 '14 at 14:15
  • \$\begingroup\$ Not so easy to replace caps, in my opinion. The power planes really suck the heat out. But diagnosing a MOSFET failure might be more of a challenge for the average tinkerer. \$\endgroup\$ – Spehro Pefhany Sep 20 '14 at 15:23

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