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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Supplies
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
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+.
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
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.
The sinks that I used for this were originally from a kit I had gotten to cool the memory on an older video card. They are old school aluminum Alpha pin sinks. The only problem I had with using these sinks was their length. They were originally intended to cover two memory chips on a video card that were spaced about a centimeter apart and that made them far too long for my purposes.
Now, some will take a sink this length and just epoxy it across several of the mosfets under the idea it will effectively cool all of them. However, most mosfets are not the same height and this will lead to too much space between some of the mosfets and the base of the sink. The best way to handle this problem is to chop the sink down to the correct size (i.e. the base of each sink will be approximately 11mm x 11mm which is the size of the top surface of the mosfets on this board).
A Dremel or other rotary tool equipped with a high speed cutoff wheel is the best way to cut the sinks but a hacksaw with a good sharp blade will work if necessary. To keep the base of the sink from being damaged, it should be covered with masking tape to avoid any unnecessary scratching of the sink’s surface. Once the sink is masked, it can be placed in a vise (or held with a pair of vise grips or pliers if necessary – the sink will get extremely hot during the cutting process so bare fingers are out of the question) and cut with a cutoff wheel.
Note: Always wear proper eye protection and a proper filter mask when using a high speed cutting wheel. Cutoff wheels often break during use and they can throw extremely sharp pieces of the wheel (as well as the material being cut) with enough force to cause serious eye damage or even blindness. Cutoff wheels also produce a dust that is a mixture of the wheel compound and the material being cut and it can be very irritating to the respiratory track.
In order to make sure each sink ends up being the correct size, the masking tape should be marked at approximately 11.5mm intervals (the extra .5mm accounts for the amount of material that will be lost in the cutting process) for the mosfet sinks. The sink for the v-reg chip is a little thinner but longer than those used for the mosfets – mine measured right at 18mm x 10mm with a slight bit of overhang on the length. After the sink is mounted in a vise, the lines on the masking tape should be carefully followed with the cutoff wheel to produce fairly smooth cut lines and reduce the amount of cleanup that is needed before mounting the sinks.
| Cut lines added to the masking | Cutting the sink with a cutoff wheel |
Once the sinks are cut and the masking tape is removed, the rough edges can be smoothed off with either a needle file or some 600 grit sandpaper. After the edges are satisfactory, the sinks should be cleaned with alcohol to get rid of any debris left from the cutting or smoothing. Note the amazingly rough edge on the sink near the top left – that is what happens when a right-handed jedi-dremel-master tries to cut a sink using his left hand while the right hand is attempting to take a picture of the entire process without resorting to a tripod…that is not a recommended cutting technique
Rough cut homebrewed mosfet sinks
To attach the sinks to the mosfets and v-reg chip, double-sided thermal tape can be applied to the base of the sinks and they can then be added to the mosfets in the same manner as used for the factory-made sinks covered above. A more secure method of attachment requires the use of thermal epoxy.
I used Arctic Alumina thermal epoxy as it does not present a risk of shorting out the mosfets if the epoxy winds up on the mosfet pins or the v-reg chip’s pins and it is a good thermal conductor. If added protection against any possible shorting of the mosfet or v-reg pins is necessary, the pins can be covered with a light coating of clear acrylic nail polish to insulate them from the epoxy. This is not necessary with Arctic Alumina but it is a good idea if a more electrically conductive epoxy is used to attach the sinks.
When mixing thermal epoxy to mount sinks that might later be removed, I normally mix the epoxy according to the manufacturer’s instructions and then add a small amount of regular thermal grease to the mixed epoxy. The thermal grease slightly weakens the bonding strength of the epoxy and makes removal at a later date possible. With Arctic Alumina, I mix the epoxy and add an amount of Ceramique thermal compound that is equal to about a third of how much mixed epoxy I have.
Then I stir it for a few seconds to get a uniform mixture. The final mixture will be strong enough to where the sink will not fall off but it will not result in any damage if the sink is removed. I was testing the so-called freeze method for removing sinks from mosfets that were applied with full strength thermal epoxy when I managed to produce the following gem.
Luckily, I was using a board that was long since dead for the test. The scratches on the side of the sink came from various attempts to twist and pry the sink from the mosfet after super-cooling it with component chiller spray. So, add a little thermal grease if later removal might be necessary.
Once combined, the epoxy mixture will dry fairly quickly so the epoxy and the sinks have to be added very quickly or only enough epoxy for a couple of mosfets should be mixed in each batch. Once the epoxy is mixed, an even, paper-thin layer should be added to the top of the mosfet with either a flat-edged plastic applicator or a finger covered with plastic cling wrap.
After adding the epoxy, the sinks are pressed onto the tops of the mosfets + the v-reg chip and given adequate time to dry. I normally let them cure for about 4 hours before moving the motherboard but they often dry much faster than that. If they are not quite straight, the sinks can be slightly repositioned during the first 5-10 minutes after mixing the epoxy by carefully sliding them into proper position. Repeat until all of the sinks are mounted on the mosfets and the v-reg chip.
| Mosfets & v-reg chip with a thin thermal epoxy layer | All of the sinks mounted on the mosfets |
Granted, they do not look as nice as the factory-made sinks but they will keep the mosfets and the v-reg chip cool. After installing the sinks on this particular motherboard, there was a noticeable decrease in voltage fluctuation. If voltage fluctuation was still an issue after installing the sinks, the power supply and then the surge protector or outlet used for the system should be checked for irregular power levels.
I once spent hours trying to track down the cause of odd voltage irregularities only to discover it was a bad surge protector that was causing all of the problems. In the event that the local power company just supplies irregular levels of juice, a good battery backup will often tame down the problem and help stabilize a quirky system. For all the fans (pun intended) of air cooling, the following is my brothers volt-modded, heavily air cooled, but not quite finished, EPoX 8RDA+.
Volt-modded & air cooled EPoX 8RDA+
Conclusion
Adding additional cooling to mosfets and the v-reg chip in the form of heatsinks is a mod worth performing on almost any motherboard that will be overclocked. The value of the additional cooling is increased with higher voltages and no motherboard that has been volt-modded should be without mosfet and v-reg chip sinks. In addition to keeping power fluctuations to a reasonable level, properly installed sinks can greatly improve the appearance of the board.