Motherboard MOSFET Cooling Guide



Kicking up the voltage to CPUs, chipsets, memory, GPUs and just about every other imaginable component has become a fairly common tactic in overclocking. Motherboard manufacturers have made increasing voltage above and beyond recommended levels easier than ever by including higher voltage settings in the BIOS options of the more popular motherboards aimed at the enthusiasts market.

Oddly enough, most of these boards still come from the factory with no cooling measures to account for the temperature increases that can result from the higher voltages. Extreme overclockers push the voltages and temperature issues further by hardwiring in resistors to allow even more voltage than the levels allowed on enthusiast motherboards.

Mosfets are power regulators
Along with a series of capacitors, mosfets convert the available voltages from the power supply into the power required to run components on the board. Because of their role in controlling power, mosfets with inadequate cooling can lead to power fluctuations across the motherboard and produce stability problems.

While some manufacturers have handled power regulation more effectively than others, adding a little extra cooling on these components can reduce voltage fluctuation and improve system stability on most motherboards. In addition to the mosfets, a small sink can be added to the v-reg chip which is usually located in the immediate area surrounding the mosfets.

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The list of supplies needed to add heatsinks to the mosfets and v-reg chip will depend on the type of sinks used. A number of factory-made mosfet sinks have appeared on the market but some spare video card sinks or ram sinks can be used to cool the mosfets and the v-reg chip with some minor modifications.

For commercial sinks, the following is about all that is needed for the job (other than the sinks of course):

  • Isopropyl alcohol
  • Cotton swabs
  • Blow dryer, hot airgun, or other heat source

Homebrewed sinks will require the above and some or all of the following:

  • Spare video card or memory sinks
  • Thermal epoxy or double-sided thermal tape (aka frag tape)
  • Clear acrylic finger nail polish
  • Masking tape
  • 3M Wet/Dry Sandpaper (600 grit) or a small needle file
  • A Dremel or other rotary tool with a high speed cutoff wheel or a hacksaw

The usual heatsink supplies

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The victim…ummm…motherboard that I am using is an EPoX 8RDA+. This board usually benefits from mosfet sinks as even with stock voltages, the mosfets get very warm. If voltage mods are performed on the board, the mosfets get downright hot. The mosfets can be seen in the upper left of the following picture (they are the black chips surrounded by the vertically-oriented black box ). The horizontally-mounted chip directly above the mosfets is the v-reg chip (surrounded by the horizontal black box).

Mosfets and v-reg chip on the EPoX 8RDA+.

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Commercial heatsinks
Installing factory-made mosfet sinks is quick and somewhat effortless. Most of the factory sinks have thermal tape preinstalled on the bottom of the sink so mixing up a small batch of thermal epoxy is not even required. The factory sinks that I had on hand were made by Microcool and they are very nice sinks. To install the factory-made sinks, first, disconnect any power source to the motherboard. Then, clean off the tops of the mosfets and the v-reg chip with a cotton swab that is slightly damp with alcohol. The alcohol should be allowed to entirely evaporate off of the surface of the mosfet before installing the sink onto the mosfet.

Mosfet surface preparation

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Next, remove the thin, blue plastic layer that is covering the thermal tape on the bottom of the sink. Once the plastic is removed, the lightly-textured, white thermal tape will be clearly visible on the bottom of the sink. In order to get good adhesion between the thermal tape and the surface of the mosfet, the thermal tape should be lightly heated with a blow dryer or other heat source. Once the tape is warmed up, the sink should be applied directly to the top surface of the mosfet with light-to-medium pressure. Repeat the process for the remaining sinks. Like I mentioned earlier, installing factory mosfet sinks is quick and easy.

Microcool mosfet sink with factory applied thermal tape.

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